I really think university presidents are the main reason we don't have a playoff. I think they feel that the massive revenue that most programs receive might be threatened with a playoff system. I'm not sure where that rationale comes from, but I occasionally read bits and pieces that this is the concern.
Agree, but I don't think the coaches really want a playoff, either. Each team woud have to play at least two more games, so that probably impacts the thinking of the University Presidents, too.