In professional stick-and-ball sports, there is no sporting reason for a playoff, only marketing reasons. There is no sporting reason to have divisions, conferences, leagues, wild cards, playoffs, or game 7's... those are just marketing... they exist solely to boost fan interest and excitement. The exact same arguments about why a 36-race points total is righteous in Nascar also apply to MLB, NBA, NHL. Baseball teams could play a balanced schedule against all the other teams, and at the end of the regular season, the one with the most wins is the champion. The only exception is the NFL, with 32 teams. They would need two divisions... play every team in your division, and the best team from each division advances to the championship game (a one-game playoff rather than eleven games involving twelve teams).
So if Nascar having a playoff is a "gimmick," it is in good company because every other sport also has its own gimmicks.