It's all about the money. Teams that can contend draw more fans. If a team can't seem to contend under the current conditions, the league/commish creates a scenario where they hopefully can. The NFL is the worst. In addition to the salary cap, the NFL sets up it's schedule so that the worst teams play the worst teams so someone can get a blue ribbon. And conversely, the best play the best so someone is saddled with a loss.
See previous reply.