Because which schools are getting invited to the SEC or B1G? As is, including us (and that's being generous), there's maaaaaaybe two schools that would bring enough revenue to make it worth the SEC/ B1G's time.
When the networks decide to kill off the rest of the Big12, Pac12 and ACC, they will only have to split all of college football into two massive pies. More than enough money will be ‘created’ by diverting it from the rest of college athletics, in a similar math exercise that Buffnik outlined from ESPN.