Haven't you ever seen somebody try to crush someone's hand with a handshake when trying to intimidate them? Or using a handshake as distraction before punching the other person in the face? That's why they are trained.
It's a bit like a front push kick or front thrust kick, depending on the impetus. The thrust is usually performed with the heel. I once had to kick in a door at a train station (It was stuck closed and some security guards were trying to kick it open, so I volunteered). Definitely had to use the...
I think it has more to do with the conditioning bare knuckle boxers had of their hands and that boxing gloves don't allow one to clench their fist as tightly.
The fact that you refer to the way you look and are angered by the girls avoiding you may be a clue as to why they are avoiding you. Maybe you should look within before you look elsewhere.
That explains why you have to hit someone 5 or 10 times in the same spot in order to finish them, instead of just once (too much aggression, not enough technique).