Sports games may not have the traditional narratives that we associate with games, but they do make deft use of emerging narrative - a term that critics fawn over when it's applied to Far Cry 3, but never recognize in Madden.
When your star player gets injured and your offensive line struggles, that's emerging narrative. Every time you take a stunning loss in Fight Night's career mode, then retrain and come back to KO the same boxer, that's a story driven entirely by gameplay and player input. Weather effects can roll in and amp up the drama in a rough fourth quarter. The player can lose his prime draft pick and end up facing off against the athlete he hoped to recruit. These are every bit as sophisticated and effective storytelling tools as Far Cry 3's wandering predators - and in both cases, the player forms the narrative internally as actions and reactions occur onscreen. So while it's true sports games don't have a set story arc, emerging narratives do occur on a game-by-game basis, and especially when you play a whole season or career mode - but they're largely internalized by the player.
Passion, Rivalry and Society
Sports aren't merely games, it's where society plays out its insecurities and invests pent-up energy. Consider the ago-old tradition of sports rivalries, for example. Though the average fan might not realize it, rivalries often capitalize on wider societal tensions that the teams represent. When you're seeing the University of Texas defensive line colliding with the Texas A&M offense, you're watching class warfare. Traditionally, UT was the older white-collar research and humanities university, while A&M was a blue-collar agricultural and military college. (That's not true anymore - A&M is an excellent research school and has a hell of a sci-fi archive.) Jokes between the two cast UT Longhorn "teasips" as elitist and out-of-touch, and A&M Aggies as country bumpkins. While rivalries take place on the field, the energy that fuels them comes from larger societal conflicts. These conflicts can be political (England-Argentina, in the wake of the Falklands War), racial (fan violence in Eastern Europe) or even religious (the Utah vs. BYU "Holy War"). I recently attended a Muay Thai match in Bangkok. The fight happened two days before a mass-protest was scheduled to shut down the city - a confrontation that's still going on, and has led to several deaths. During the match, you could feel the heightened tension in the room. The city was spoiling for a fight.
If you want a current example, consider this year's Super Bowl. What does pot legalization have to do with football? Nothing. But that doesn't stop anyone from pointing out that both states playing have legalized recreational marijuana.
Sports allow a society to diffuse this energy in a safe space, for there to be a confrontation without anyone being seriously injured. (Though these same tensions can boil over into riots or fan violence.) Again, this is something that sports games lack, since without an audience games become less of a communal experience. Indeed, unless you're especially invested in the history of a particular rivalry, social factors don't have the same sway.