I don't see why kicking dirt in someone's eyes should be any more impossible than hitting them with a weapon.

Ok, maybe if somebody had the ability to not exert themselves while fighting, they'd be so quiet that you wouldn't know where they are. But even then, it might be possible (you're swinging your weapon around wildly trying to parry, and either your weapon or you gets hit -- all of a sudden you have a rough idea of where they're at -- not a great chance of hitting them, but not impossible either).