This link makes a great point.
The SEC doesn't make tons of money right now because we have the best media footprint in the biggest media markets. We make tons of money because we have the best football teams.
People in other markets don't need to tune in because we have a team in their area that they cheer for. They tune in because they want to watch the best teams play football - just like I will watch 7 Stanford/3 Oregon, 1 Oklahoma/9 aTm, 11 Wisconsin/10 Nebraska, etc.
While it's good to add new markets (St. Louis, Raleigh, Pittsburgh, etc.), it's also very important to keep the quality very high so that people all over the country will watch. Not that F$U will ever happen - but that's the argument for a team like them. They don't increase our footprint, but the demand for FSU/UF, FSU/Bama, etc. would be very high and thus lucrative.