At a university level, they're a black hole of student fees. Have you looked at a budget? If they bring in much more than they spend why do student fees cover hundreds of thousands of dollars in insurance premiums for the few students who are participating? Why aren't the programs able to cover that themselves instead of fleecing the entire student body?
I've looked at K-12 sports too. It's a sea of red ink. Those should be community programs following a little league pay-to-participate self funding model, not the domain of school curriculums and tax dollars.
When I was in college (back in the early 90s) at the University of Florida, our sports program actually made money for the school.
Gatorade, ESPN television rights, merchandising, ABC/NBC/CBS/Fox television rights for the Gator bowl, etc, etc, etc.