If I had to guess, it’s probably that there are more schools in other sports that don’t compete in football?
Most of the teams in the SHAC don’t have football. In the SOC Clay, New Boston, Ironton St Joe, Western, and South Webster do not have football. That’s an additional 14 schools in the Southeast region for every other sport other than football. I’m sure there are other regions where that also happens, but it seems like it’s more common in the Southeast.