Mainly because you generally need to make some big plays to win in the playoffs, and because they could run a power running, ball control offense with almost any quarterback. Seems a waste to have a generational quarterback and not feature thenoffense around him. Having a running game is great but it is not enough in the playoffs. You still need to threaten with an offensive passing game, including chunk plays. That is, unless you can just dominate the opponent with a dominating defense.