16 teams makes for a nice 4x4 divisional setup, but it's the fans looking at that, not the schools or the conferences. They're looking at money, and will not look to take in less in order to make a pretty org chart. That goes for the 4x16 conference setup as well.
It may work out nice for postseason, but unless forced on them from above (e.g. NFL commissioner), it has to fulfill the needs/desires of the decision-makers (i.e. school presidents and conference commissioners), and right now, it doesn't.