The main difference is that all other college sports championships are actual NCAA championships, while college football is done by the BCS, which is NOT an agency of the NCAA. The reason that is the case, dates back to the lawsuit back in 1984.
So to get a playoff, we will need the BCS to vanquish and the NCAA to proved the championship as it does with every other sport. But don't look for that to happen. Read all the rules about the playoffs for division 1 FCS, Division 2 and Division 3 football. The NCAA rules clearly state that in those divisions, no corporation may sponsor a game and that no corporate logos can be displayed in the stadiums where a playoff game is being played....
so there ya have it. It IS all about the money and sponsorship.