Another reason the best skiers on any given mountain are typically racers: they spend a lot of time doing skill building and strength building exercises. Most skiers, even the best ones, aren't going to spend 60% of their time doing drills: they want to go ski. I know plenty of skiers who ski all the time, yet are pretty mediocre, as they don't ever try to improve; instead, they just go up and ski, which is fine, but it doesn't necessarily make you a better skier. As a result, they can cruise just about any terrain on a flat, intermediate mountain like Bachelor, but get schooled on steep, technical lines or any other type of black diamond terrain. Just as most runners just run for fun, or even run hard from time to time, but elite runners are doing intervals and structured workouts 3+ days a week, as are golfers. The best golfer at the course where I grew up (and our high school assistant coach) spent 70% of his time in either the range or the putting green, putting in the constant repetitions required to be a sub-scratch golfer.
A good friend of mine was a racer in college, and one of the best skiers locally. When he skis, he still has that mentality: every day, he gives himself something to work on and improve with, even though he is free skiing. He calls it "focused free skiing". Whereas I know other skiers that actually have regressed, as they move away from racing and, due to lack of any sort of focus, end up with bad habits. I bet any of the top free skiers we see, whether they came from a race background or not, learned how to ski well and do plenty of upkeep to make sure their skills are sharp.