The key word is "reasonable". What YOU think is reasonable and what I think is reasonable are two different things. I do think there is some SAFETY benefits to having fall sports...
1) The activities can be truly regulated. Whether that's mask mandates and social distancing (for players and team personnel), or reducing if not eliminating fans, a school (college, HS, or MS) will have an easier time than everyone making up their own rules.
2) It keeps the athletes active, tying up anywhere from 2-4 hours of their day at least, then they have to do school work. Compare that to NO athletics, so after they do their school work, what are they going to do... hang out with friends.
3) This probably applies more to big time colleges than lower tier and HS... testing. As you point out, even regularly testing twice a week is better than what regular people get. How nice would it be if everyone got tested going into work 2x a week (at least). Of course, to make the testing worth anything, you've got to get the results back within hours if not a day, a week or more later and it's basically worthless.
PS... when I say everyone gets tested 2x a week going into work, I think they get the test and continue on to work. If they find out they're positive within hours or the next day, then they quarantine. And this would be for asymptomatic people. If you have symptoms, you don't go into work.