You assume just because the PAC 12 has large media markets that there will be a natural following of the local college teams. This has been proven false time and time again in California. First, PAC 12 attendance in the California markets is atrocious. Second, the PAC 12 has struggled to get cable and satellite providers to carry the network. Third, most of the population base consists of transplants who have other followings.
You know what those three things tell me? Not enough people care about PAC 12 football. The ACC has a similar problem. That is quite different from SEC, B1G, and Big 12 schools where college football is a way of life and the entire state tunes into to see their teams.