Any player who actually understands the concepts of a character progression based game will tell you that, due to mechanics/abilities being drastically different between early/max level, and newly learned abilities changing mechanics/the way you play every 5-10 levels, very little proper learning is done prior to max level.

Take your black mage friend for example. Black mage plays very differently at level 10 than it does at 50. I'd rather he still be learning/open to learning how to play properly when he gets there than stuck in a level 10-20 playstyle mindset. Too many players have the mindset of "This how I learned to play early on, so it's just how I play."