It's because he is actually the 1,000,000 dollar man, with shoulders made out of car pistons, that power his arm with all of the force of Rampage's ass.
So you want to box like RJJ or Sugar Ray Leonard without using the power that they used? You will get hurt in the ring if you do that. I'm assuming you like to leave the fight in the hands of someone other than yourself as well since you won't be KO'ing anyone.
Also could you tell me how Cotto, probably the best body puncher in boxing right now, hits so hard without using his hips. I would really like to hear how he does this.
As far as RJJ and SRL, those are guys that, like Tyson, Ali, Mayweather and just about every other top tier striker (not just boxer), use their hips. Thanks for adding more names to our already excessive list of guys who actually know how to throw punches.