I think part of it is just the nature of the sport.
Golf can go 100% without a "bubble" because social distancing is easy and it's a personal sport so it's basically just a player and his caddy in close contact. Something like baseball is not doing well because even there there's a significant amount of distancing, it's still a large team of players being together. Basketball is doing great with a bubble, but probably couldn't exist without it. Basketball requires extremely close contact.
Football is basically a perfect storm of bad for this virus. You have very large teams (roster of 53 in NFL, 85+walk-ons in NCAA), coaching staffs, trainers, etc. Neither the NFL or the NCAA is creating a "bubble", and you really can't do that with the NCAA because these players need to go to classes too. And you have absolutely insanely close contact basically on every play.
I said last week imagine if one player on the OL is asymptomatic but contagious on game day. That player will be in the huddle with his teammates on every play. That player will be blocking numerous defenders in very close contact, breathing on them, etc. Especially because defensive lines rotate a bunch of players through. That player will end up in piles with his teammates and opponents.
One contagious player would lead to dozens of infections IMHO. There's no way to play the game with distancing. There's no way to create a "bubble". And because there are SO many players, coaches, etc (>200 individuals at a game counting players, coaches, trainers, officials) the odds are exceptionally high that SOMEONE will have the virus.
An infected player, on the field, in the game of football... That's a superspreader event, and given that you may not know until several days after the game that the infection even existed, the amount THOSE newly infected players might infect, both on the team and around the campus, would be insane.
I just don't see them going forward with it.