First of all, check this out:
https://stadiumjourney.com/news/stadium-journey-ranks-the-fcs-stadiums
I understand what you are saying, but everything is relative. Sure, football weekends at USD can't compare to football weekends at Alabama. But, I think you are kidding yourself if you think that it doesn't matter at all.
Imagine a kid who has narrowed down his or her college choices to University of Dayton and Xavier University. There are pros and cons for both. I can see a certain type of kid saying that a pro for Dayton is that it has home football games to attend, can tailgate at, and can contribute to school spirit. The same sort of kid might even consider a con for Xavier being that they don't have a football team.
Lastly, everything really is relative. The football scene at Montana might not approach that of Alabama or Illinois, but how many football related pre and post game parties and how many tailgaters do you really need at a school of 8,000 undergrads before it becomes a fun scene not to be missed relative to everything else going on at that school?
Sure, if a kid is looking solely for the football social scene, pick Alabama over Montana for the sheer scope of it. But if a kid is looking between Montana and Creighton or Montana and another school with less of a football social scene, I can see a certain type of non-football playing kid picking Montana because s/he wants what Montana can offer socially that the other schools can't.