The university I went to is in the top 20 (top 8 when I went)(this is just for context not to start an argument about rankings). The school is also in the top 20 in endowments.
When I was there they did an analysis of alumni donations. One thing they found out was that if you did 2 or more activities in high school you were likely to do 1 or more activities in college. (these numbers are ballpark) If did ANY activities in college you were around 60% more likely to donate to the school. If you did NO activities and just took class you were only 20% likely to donate. If you did MORE activities you were even more likely to donate. The amount of your donation was related heavily to your income and found to be an independent function from your activities.
Thus the school decided that recruiting multi-sport atheletes to play Division 3 sports (which we were) was revenue positive for running an athletic department. Their goal was to provide a positive feeling at all the sports so that everyone felt good about their experience. So the school got very into (even to the chancellor level) attempting to be on par with stanford's numbers in the Sears Trophy (now the ncaa directors cup) for most National Championships in a year. Which means you have to be good at pretty much everything, golf (m&w), tennis (m&w), swimming (m&w), volleyball (w), football, basketball (m&w), etc. And that's what they did.
I'm not saying this is the only reason they did what they did, they were very genuine about providing great experiences for the student athletes as they should if they're doing their jobs.
Anyway the overall point is that some schools also focus on alumni donations which ARE driven by school loalty, which are driven by sports. One could consider people buying school athletic merch as a form of alumni donation.
I'm not explaining or excusing why college sports it the big business it is in D1 as it is. I've got problems with that as well, but mainly I think the schools should be required to provide a real education for the players at ANY time in their life post graduation and some kind of revenue sharing.