If colleges and high schools can have their own "fight songs" then professional teams should have theirs if that is what they want and the same goes for toddler beauty contests, arm wrestling championships, rodeos, hot dog eating contests etc.......
When else then would the average American child ever even hear it played?
I agree: If high school graduation commencement celebrations, or other official academic events, always began with the anthem, we wouldn't need to have it played at football games.
Regards,