If anything, the evolution of humans as bipedal creatures should have made the legs into the weapons of choice, since they are not only stronger and larger but can be wielded with momentum for increased force. But the legs make for poor weapons because all the vulnerable targets are up high. While the most direct way to hurt someone is actually a straight movement towards someone, our limbs are designed to swing and swivel, not shoot out forward.
If hands were for punching, then the tissues attaching our arms to our bodies would have been designed to issue strikes faster and more powerfully. Currently it's very difficult for humans to issue incredibly rapid strikes with power; we have to use our lats, core, legs, and hips to rotate our bodies to increase momentum in a punch and line up the shoulder with the target, lest you deliver with reduced power. In contrast, kicks can be issued just as fast and with greater power, so one would think that naturally humans would have gravitated to kicking each other rather than punching, but the opposite seems to be the case.
IMHO, the most ideal strike a human can give without injuring themselves would be from the shin or heel. If you look at animals that don't have sharp teeth or claws, often they'll use their hind legs in a kicking motion to provide the most powerful hit, while moving their sensitive head/neck/chest away from the target. A few human groups developed fighting styles this way, but for millenia we've still been fighting standing up. I can only assume this is because we got so used to being bipedal that we adapted our fighting to it. I think our evolution probably prompted us to develop new ways of fighting that were comfortable to our bodies, rather than vice versa.