Florida Attorney General Ashley Moody announced an antitrust investigation into the College Football Playoff Committee yesterday. The unprecedented move
siniardlaw.com
This discusses it a bit in relation to FSU being shut out of the four team playoff a few years ago.
The conferences, plus Notre Dame, all have to agree, at least for now, on the format of the post season. If there is collusion to prevent access to the postseason the courts may not find that to be legal.
By continuing to have the lesser conferences have access, it can shield the B1G and SEC from legal action. That's not why I think there should be equal access - I think there should be because it is one level of football, and at all other levels, conference champs get autobids. But I do think it's why we wont see a major change right now.