There's no pull to get them. BYU would be invited before them.
Pac12 isn't looking to cover half the country. Texas and Oklahoma are pulls for the teams more than the new eye balls. And regarding Utah, they were invited not because of size but as a link to CU.
CU was invited a few months as a play to keep Baylor out (they were thinking they had the 5 non-religious schools from Texas locked up, so CU was a quick play to block Baylor). Once the 5 Texas schools back out (or, the play by Texas got UT what they wanted from BigXII), Pac12 was stuck at 11. Utah became the 12th, and SLC market was a secondary benefit as they rolled out Pac12 network.