Well, I would like to compare this with RL.

If you hunt rabbit for many years, you will eventually become a master-rabbithunter. BUT, no matter how many rabbits you catch, you can't catch a bear with the same thechniqe.

You become a master at killing sword cost monsters, but slaying 1000 of them won't help you in killing one amn-monster.

To make it as you would have racial enemy-experiance or something would make things to complicated, so a cap became natural for the developers.
Don't remove it. I think it is much more fun with than without.

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All hail The Wizard!