Well it wouldn't make the enemies stronger, just add more of them. Also this is not like RPGs were enemies level up with you. Its just that certain enemies are tougher than others (for instance even at your current level you could fight something quite powerful, but I am not mean. Vice versa as well as even at high level I could pit you against small fries like these). 

What makes this system nice is that even small fry enemies are a threat, no matter what level you are. If they manage to hit, they still deal damage, and even "leveling" is more meant for upgrading your abilities, not really making you twenty times stronger as it does in some games. 

So even if you get to a point where you earn 100 XP or more you could still find yourself having a tough time against small time bandits or other small fry enemies.