Why? Those teams would help since they are in recruiting areas that make sense for us. Playing the PAC 12 teams is nice due to the Rose Bowl affiliation, but not sure recruiting nationally is in the plans for us in the near future.
Because I have no interest in playing a glorified Big East OOC schedule every year. I'm a fan, not a coach, so I want to see interesting games, not games that will maybe, possibly, some day land us a recruit. I have no problems mixing in some ACC teams in Florida and the like, but no interest in watching all "[big] east rivalries" all the time.
Selfishly, PAC games are easier for me to travel to and the timing lines up better with my schedule, but that's very secondary to the other reasons stated.