It started that way, but like anything else it’s become commercialized by sponsorships. In this case, the DoD. Whether it’s the song itself they’re paying for or the ceremonies surrounding it with the color guard, flyovers, salute to service, etc., the league would be missing out on revenue by nixing it, so that’s a non-starter. (Of course not having it now would cause an even bigger uproar from he “look at me” patriot types who demand players stand for the anthems while they lie on the couch and drink beer.)