Snap? As it a snap of a whip or a snap of the arm, or what?
Are you talking about snapping your fist back after striking? If you trained then you'd see the reason why it works and why the untrained shouldn't give out advice on fighting.
You pull back so you can hit again faster. If you push your punch even more, then you're not only hurting yourself but you're trying to push them, not HIT them.
think of how a bull whip works, its only like 4 ounces but can utilize 750 Ibs. of pressure, its using speed for power rather mass.
Eric has a good point.
