My guess is that the NCAA doesn't want to fight the attendance battle, that will be saved for another day, if ever. They have bigger fish to fry; safety perception, players leaving early, chicanery and cheating under the table a la the Wake Forest fiasco etc.
A lawyer friend told me years ago that the NCAA would never enforce this attendance requirement because it would open them up to a restraint of trade law suit. He further said that he would take the case as the plaintiff's lawyer in a heartbeat.