This is a big event for some people that have to travel great distances to play. 2000pts is a way to bring all the toys you want and have fun. I come to the OFCC because it is fun. Do my games at OFCC always make it to turn five or beyond? No, but as long as my opponent and I are having fun who cares? If it wasn't for the OFCC I would have never bought, built and painted my stompa. You have room for that cool, fun model in a 2000pt list.
I'm sure I would have fun playing smaller games, but smaller games limit your choices. So if your goal is to have fun why limit yourself?