Anyways...
We reach the playoff conclusion for several reasons
1. The inherent *need* to crown a champion on the field. Sports in this country (in general, really) are about the draw of competition, of winning and losing. It brings about closure to the season and a resolution to the season-long conflict that has been playing out on the field. Any champion who is determined by a series of direct wins and losses in a playoff-type system which includes as many championship-caliber teams as possible (I put 8 as the perfect number, but that's up for debate) will be viewed as a more legitimate champion.
2. The fact that schedules are massively unbalanced in college football. If every single team played a 120-game round robin with each other team, it would be quite easy to crown a champion without a playoff (Just take the team with the best record!). But prior to the BCS even, situations would arise between an undefeated team who clearly played an inferior schedule to a 1-loss team with a very good loss. How do you decide a fair winner there?
3. The variance that exists in football means that the best team in the nation can lose 1 or two games just on how the ball bounces on a particular day, where a team like Notre Dame in 2012 can squeak out a couple of lucky wins and finish undefeated even though they are clearly not a strong team. For this reason, including more teams is better because it includes any teams who may have been on the wrong side of the bounce of the ball once or twice (or officiating, like Michigan State this year!)
4. The business that is college football is gigantic at this point, and a big extravagant playoff series will create huge attention, viewership, advertising opportunities, ticket sales, TV contracts, you name it. Money is certainly part of the equation.
Of course, that same variance means that the winner of the playoff will be more variable than crowning one team by a vote after the season. The 4-seed might knock off the 1-seed. It could happen! And probably will at some point! But that's outweighed by the fact that deciding the winner on the field gives greater legitimacy to the eventual champion. If that 4-seed Michigan State had knocked off 1-seed Florida State this year, we couldn't really question that result. They won on the field, fair and square. If somehow MSU's 12-1 season was massively more illigitimate than FSU's 13-0 regular season and the regular season is rendered inconsequential by such a possibility in your mind...well I don't know what to tell you. You probably won't be happy with any system.
Plus the playoff will be fun!