Not really sure what you're talking about. There were a few "big" girls on the dance team at my school. And on the softball team. And the soccer team.
I think more often than not, the "bigger" girls aren't typically found on high school teams because they simply can't always compete at the same level as the more athletic body typed girls. Not everyone gets to make the team. And if you happen to be the slowest kid, it doesn't matter what your size is...you probably won't make the cut. 4951