pros do it is because the number of teams are limited. You don't see the NFL, NBA, NHL, and MLB playing teams from other leagues (think conferences at the college level) during the regular season. Whereas in college you see schools playing teams from both other conferences in the same division level, other NCAA division levels, and even NAIA schools. I would be very surprised if that aspect change assuming college athletics received antitrust exemptions. Now if the P2s decided to do their own thing, then they would just schedule games among themselves. However, for the rest of DI, DII, DIII, and NAIA schools, it remain business as usual in terms of scheduling.