If you've ever been hit hard to the body, you know how bad that punch feels. Bad is an understatement. Hard body shots can take the life right out of you. They can freeze you right up, leaving you feeling paralyzed with no wind.
Even if the body punch doesn't knock the wind out of you, it will wear you down in the long run. That's why great fighters utilize a body attack early on in the fight. The results of their work are always immediate, but they are telling in the middle, to later rounds.
Landing solid body shots opens the head up for power shots. The motto in boxing is, Kill the body and the head will follow. Fighters that have a hard time scoring with head combos will mix in a solid body attack, to open up those opportunities.
If the fighter blocks your punches, don't fret, your still wearing him down. Landing punches on the opponents arms, will cause them to bruise and even feel to heavy to hold up. Rocky Marciano used to break bones with his hard and viscous body attack.
That's why good fighters stick with the body attack. Even if the punches are blocked, they"re still doing damage. If a fighter can't keep his hands up, what good does that do him?
It does him no good. It leaves him busted up, and beaten.