because it's part of a "conference" agreement.
this michigan thing being before the PAC/B1G agreement is a big get for them. nobody ever comes to just play utah. why would they? look at their history and tell me the last time a ranked OOC team came and played at RES?
i don't think any team that has EVER been rated in the top 10 has come, and maybe you could find one that was rated in the top 20 years ago. they did get pitt to come once and they went there for a home/home, but it's pretty hard to take ANY big east team seriously outside of newcomer boise state.