You can't magically create a great player by holding a kid back. It may appear that a mediocre player is a better temporarily, but that will only last a little while. If you hold a great player back, they will continue to be great and look amazing. Problem is most of the kids being held back now are not great, just average. In a few years they will be average again. If they happen to be recruited the majority will ride the bench. Cream rises to the top, no matter how hard you shake the milk!