There are many reasons (money, greed, the appearance of power, exclusivity, the hierarchy of the current system) but the #1 reason and the true driving force in college football is Recruiting!!! With the way it is currently set up, only teams from the P5 conferences will get into the CFP. If they create a playoff that gives an opportunity to all 10 conferences champions and 6 at large bids from the remaining top ranked teams and seed them to create a 16 team playoff, then the leverage for the P5 to recruit is gone. Will Hall can go into a recruit's home and say, "If you come to Southern Miss you have a greater chance to play in the CFP than if you go to a Ole Miss, Miss State, Arkansas, or even an Auburn."
Once a 16 team playoff is started the you will begin to see more money come into programs in a CUSA and Sunbelt and that will even out the playing field. It all starts with recruiting. That is why there will never be a true 16 team playoff.
What are your opinions?