I wrestled 215 and my whole team was always shouting at me "shoot!" and I never did, but then in one match, with about 5 seconds left, down by one in the consolation finals, I shot in without anyone saying anything... and I did it perfectly. My whole team was in shock. That was the first time I can really remember ever doing that in a match (I started wrestling in 7th grade).
The reason you don't see the fat dudes doing anything like that is because they aren't as strong as the lighter-weights COMPARATIVE TO THEIR BODY WEIGHT. It's not easy to move when someone is putting anywhere from 200-275 pounds of weight on your body.