The current playoff format means that at least one P5 will be left out each year. The SEC thinks it will get 2 each year, meaning only 2 other conferences will get one spot. Not having a clear conference champion will make it easier to leave you out. A Big 12 team might have to go undefeated in conference to even make the playoffs. That is pretty hard to do in P5 conferences, since no Big 12 team has been dominant since Texas won the NC.