[Kaimetsu]

The primary problem with magic is that you can't see far enough, and people run too fast. Or both. Whichever. There'd need to be lots of holding and healing and escape spells and things to make sure mages don't get their faces beat in, but then there'd also need to be mechanisms to stop the mages from just turning tail and happily running away when the going gets tough.

And the NPC bad guys are too slow.