The thing about bodyboarding compared to surfing is that you can basically bodyboard ANY wave including shore break, rough choppy water, and not have the lifeguards get nearly as pissed at you. The important thing though is the shore break part because on my beach any wave smaller than like 5ft will shore break unless driven by a long period swell. This is why I bodyboard because of my environment, and because the boards are cheaper, breaking them doesn't really matter, its easier to just jump in, and i just feel more free on it with less dead weight to worry about when wiping out.
it's because if somebody paddles out and it's not one of your buddies you honestly wish that they were not there, some one else to share the waves with that might end up in you not getting a wave. we (surfers) often hold a belief that body boarding takes less skill then surfing so you are not worthy of the wave (not saying that it's right). I've seen surf snobs do it to other surfers all the time because of lack of skill.