I looked at the top 20 prospects here in Arizona for 2015.
17 are committed, with 10 of them signing for schools outside of Arizona (2 signed with Utah and 2 with Colorado) instead of U of A or ASU, which are both pretty solid right now. Only 1 of the top 7 stayed "home" with 1 still being uncommitted, so at least 5 of the top 7 will play outside of AZ.
Sometimes it is the allure of more "prestige" (A&M, Nebraska) or situation, or just wanting to leave the state as Boise St and K State both have commitments from players in the top 7.
It may be a little different expectation with BYU and LDS recruits, but it's hard from some kids to pick BYU over USC, Stanford, etc and will always be that way.