Because if you play in those leagues you play your "good teams" in your conference slate. Mid majors must play an inverted schedule (effectively a high major-level OOC) to counteract their mid-major in-conference. You are allowed to play Quinnepic and Wofford at home, in November, if you are taking a one week road trip to Syracuse, UConn, and Pittsburgh in February.That is the biggest wrong with the whole NCAA.
You can be in the Big East and its apparently ok to play a soft non conference, but you better not in any other non BCS, and god forbid you lose even one game that is played v a BCS school or trip up against essentially anyone and never ever at home if your not BCS.
Why is it good for one NCAA team but not another? Again conference affilation does matter.
The entire thing is completely rigged and staged and expansion will just expand the rigging and staging to more BCS's.
Conversely, high majors play mid-major OOC schedules because they play high-major in-league.