All right--let me throw another curve into the mix--a little something more to ponder in regards to Bud's question.
Consider what happens to the trajectory of your body (center of mass) in a turn when you move it forward (relative to your feet) to press on the boot tongue or ball of the foot. That forward motion momentarily straightens the curve (increases the radius) of the arc the body had been following, and also increases its speed. At the same time, the increased pressure on the ski tip tightens the radius of the curve the ski tries to carve, and may well also cause the tail to skid out due to decreased pressure. So the skis tighten their radius and/or suddenly slow down, as the body increases the radius of its arc and speeds up. Their trajectories move in a quickly converging collision course....
Can this be a good thing? Have you ever seen it happen?
Another thought question: Imagine a garden rake (T-shaped thing) standing with the rake end on the ground and the handle straight up. For some reason, you decide that you'd like to add pressure to one end of the rake (one arm of the inverted "T" at the bottom of the handle). What do you do? Tip the handle toward that end, of course--pushing the one end down while lifting up on the other end. That would be equivalent to moving your body forward of your feet on skis to add pressure to the tips (while reducing pressure on the tails). Now, imagine that garden rake lying flat on the ground. Now what movement would you need to make to add pressure to one end of the "T"? Pushing the handle toward it wouldn't do it, would it--it would just turn the rake, changing the direction it "points." When it's lying flat on the ground, the movement that adds pressure to one end is, of course, twisting the handle.
So the more we incline (lean) into a turn, the closer we come to being like the horizontal rake lying on the ground. The effects of our movements change completely--when upright (vertical, or perpendicular to the slope), turning the legs changes the direction the skis point, while moving forward and back (relative to our feet) changes the fore-aft pressure distribution on the skis. But if we were lying horizontal on the slope, "fore-aft" movements of the feet change the direction the skis point, and turning movements of the legs affect tip-tail pressure on the skis. All turns fall somewhere between these two extremes, so it is virtually never as simple as just "moving the hips forward," or pressing forward on the boot tongues--which can have the adverse (and in fact, potentially disastrous) effects I suggested above.
Finally (well, maybe!), consider what your movement options are when you are pressed hard against the fronts of your boots. Which direction do they press on you? If your boots are stiff, "being forward" against their tongues is a lot like running into a wall. Ironically, "being forward" pretty much prevents moving forward. Have you ever tried skating on alpine skis? Do you continually press forward on your boot tongues? Give it a try, and see what happens!
Being "forward," never getting "in the back seat," keeping your hips forward (of your feet?), pressing on the boot tongues, and so on live on in the dogma and ancient doctrine of ski technique, along with so much other typically unquestioned (but inherently questionable) "conventional wisdom." Snowboarders, on the other hand, with a much shorter history, are not usually so afflicted by limitations imposed by dogma and tradition--they have no problem with pressuring either foot as necessary to make their board perform as desired. Like so much dogmatic "wisdom," I urge everyone to question and challenge it. Explore it with an open "beginner's" mind, and explore its opposite as well. Don't believe anything you hear. Don't even believe everything you think! Don't disbelieve either, of course. Question and challenge everything, And let us know what you find!
Best regards, and Merry Christmas!