It's a bit out of proportions. Grinding up to level 60- experience is far more than what is needed to master a job level 60. Especially because you actually get a sense of your job in the latest levels. From 1 to 50 it is clunky most of the time.
And there are players that don't buy job potions and play equally bad at max level.
I think it's ok the way it is, you don't get max level, and the game itself offers a lot of content to train your new job. You can't expect people to do it of course.