OK--got an answer? Does your answer sound anything like "to slow down," "to control speed," or even just "for control"? If you're like 99% of skiers, it does. And that answer is the most limiting thought in all of skiing. It isn't "wrong," of course, but it will prevent your turns from ever approaching the expert's carve.
Why do you turn a car or a bicycle? Why does Alberto Tomba turn? It has nothing to do with speed control, does it? I didn't ask why you hit the brakes! You turn, of course, to control line, to keep it on the road, to go precisely where you choose to go and in the precise direction you want--not to slow down. Your skis can work as brakes or as turning tools, but not at the same time. The two movement patterns are contradictory. So to think like, and begin to carve turns like an expert, you must stop trying to control speed. In fact, you must want to go faster every time you make a turn. That's what will happen, naturally, each time you turn your skis downhill without the brakes on. So if you're trying to control speed and a good turn makes you go faster, you have a conflict. You can solve the conflict two ways: you can brake instead of turning, or you can change your thinking and ski like an expert! The fact is, experts are never in control of their speed, at least not unless they have to be. "WHAT!" you say? That's right--experts are in control of their LINE, and that is all they want and need to control--never speed.
So how do experts control speed? They choose and ski a line that prevents them from ever needing to control speed. My definition of good skiing is "skiing a slow enough line as fast as you can," at least when you can. There are two--and only two--ways to slow down, on skis or anything else. One is to increase friction or resistance--hit the brakes, fall down, drag your poles, hit a tree, etc. The other is to go uphill. There is no third way. In good turns the skis go the direction they're pointed--there is very little friction. So those experts skiing "down the fall line" must be either: a) going faster than you think, b) not making as good turns as you think, or c) completing their turns more than it appears. If they are really good, the answer is probably a combination of a) and c). Experts choose their line deliberately. Then they use their skis to trace that chosen line. Every turn is shaped with precision and purpose. If you choose the right line (a "slow enough line"), you will never ski any faster than you want, no matter how slippery your skis and how clean your turns. And you will rarely feel the need to brake.
How do you ski a slow line? You complete every turn. If each turn is part of a circle, I mean simply gliding far enough around the circle that you eventually slow down enough that you feel like you are going too slowly! Remember--the prerequisite for a good turn is that you must want to go faster. The only time I want to go faster is when I'm going "too slow." So your turn is finished the moment you want to go faster, and not a moment sooner. For a very good skier who wants to go slowly for some reason, that often means skiing each turn back UP the hill before starting the next turn. But they don't do that, you say! They ski down the fall line, barely turning. If you believe that, you're being deceived. Like I said--if they're skiing a fast line and making good but incomplete turns on anything with decent pitch, they are going fast. Or else they are braking. Or else their skis need waxing badly. If you look closely, you will see those true experts are probably completing their turns more than you thought, maybe even going back uphill. Look at their tracks--they'll be easy to see, arcs engraved in the snow. (If not, the skier was skidding a lot and not as good as you thought.) Because good turns are so smooth and continuous, and involve no harsh movements and little skidding, it can be deceiving how complete they are. And remember that in moguls, each bump is an opportunity to glide up a little hill without having to complete the turn back up the mountain. Also, because carving, gliding skis are MUCH smoother and more stable than skidding (braking) skis, speed doesn't look--or feel--nearly as fast. So the skiers look relaxed, balanced, happy--not at all like they are going too fast or trying to slow down. Because they're not--they are not trying to control speed. Period.
Also, they probably aren't going far across the hill with each turn. It is a false notion that "going back and forth across the hill" slows you down. It doesn't. Going UP a hill is the only direction that slows you down. Many misinformed skiers habitually traverse across the hill between turns. Imagine the turn as a clock face. Say you begin the turn from a stop, at "12 o'clock." You turn down the hill--1 o'clock, 2 o'clock...at 3 o'clock you're heading straight downhill (and gaining speed). 4 o'clock, 5, 6, 7 o'clock--now you're heading back up the hill. It's unlikely you'll get much past 9 o'clock before you glide to a stop. The skier who turns to, say, 5 o'clock, then goes into a straight traverse, gains speed all the way across the hill. Finally, at the other side of the trail, he must hit the brakes. Expert skiers link turns seamlessly. They glide around the clock face until they want to go faster, then they relax, turn downhill, and enjoy the ride and the acceleration. They complete the turn, then do it again. It doesn't matter, by the way, how BIG the turns are or how many you make--circles come in all sizes. It matters only how far around the clock--or watch--face you ski.
So expert skiing--and the carved turn--is a state of mind. It is an intent as much as a skill. A good turn begins as the desire to follow a chosen path on the snow as fast as you possibly can. If you choose a path that leads up a hill, it matters not how fast you want to go or how good you are at gliding and carving--you're going to slow down. If I want to slow down, I go up a hill--as fast and far as I can! If there's a hill ahead of me, I'll go straight to go up it. If not, I'll make a turn and go back up the same hill I just came down. Note the word "go." Even stopping should be an attempt to GO--up a hill. Turns are always "go" thoughts. I turn to "go that way"--not just to "stop going this way." Turns are never defensive, always offensive. They are not a way to avoid going downhill--they begin as the very intent to go downhill as fast as gravity will pull.
If you feel a need to slow down or control speed, you've already made a mistake. The only time I want to slow down is when I'm going too fast, right? Experts may ski very fast, but they never ski "too" fast. Too fast is a state of mind that you must avoid like the plague. Skiers who think like experts always want to ski faster on any given line. Even Tommy Moe, at 90 mph, feels too slow--he'd go faster if he could.
Here's the great news for us all: you need not BE an expert to think like an expert. Nor do you need to ski fast. You just need to ski a line that is slow enough that you want to go faster all the time. You need to ski "too slow"--like Tommy Moe. You need to strive for speed control from direction and avoid speed control from friction. If good skiing is "skiing a slow enough line as fast as you can," we can all ski a "slow enough line." The "fast as you can" part depends on your skill--obviously a more skillful skier will be able to ski any line with cleaner turns, less skidding and friction, and more speed. But even a novice's wedge turns should be attempts to glide as precisely and cleanly as skills allow along the chosen path. A novice thinking like that is thinking like an expert, attempting the same thing Alberto Tomba and Picabo Street are attempting. And moving closer to expert skiing with every turn as skills improve. Technically, they ski much better than those "pseudo-experts" you described, who dash down black diamond runs making linked "hockey stop" braking movements. The "correct" novices may lack skill, but they are doing the "right thing" as well as they can, which is EXACTLY the same thing Alberto Tomba does.
Mind you--I am not saying that braking is bad. Only that it is not turning. Braking skills are essential (although ironically, braking becomes more dangerous the faster you go). Braking is good whenever you truly need to slow down or stop and can't go up a hill. Braking is an important skill, but it is a bad habit.
Nor am I implying that there will be no skidding in a good turn. All turns involve some skidding, just as cars slip or squeal at least a little as they go around curves. The key is that good skiers (and drivers) don't usually TRY to skid. Their turns don't begin by pushing the skis sideways. Again-it's a question of intent. If you've ever done "donuts" in your car in a snowy parking lot, you know that you can drive a car in a way that causes the back wheels to slide out. But you usually try to avoid that. Most skiers push their tails sideways, forcing a skid. Good skiers don't, although their skis may still skid a little, or a lot, depending on skill level, ski tune, snow conditions, steepness, and speed.
Well, if you've read all this, I've either planted a new idea, or totally lost you. Or else you're one of the 1percent of skiers who thinks like an expert in the first place. So why do you turn? It's to control direction! And you turn because real turns feel great! They are not a means to an end, a way to survive a run. Good turns are an end in themselves. Most people don't make good turns, no matter how much they practice, simply because they aren't trying to turn in the first place--they're trying to control speed. Leave them behind--think like an expert!