I think he can be allowed to have some required meetings and make some team rules...but I also don't think he can have the power to just say "none of you are allowed to go to bars ever! none of you better be out past 10 on any given night."
they're legally adults. they have to make these decisions of what's right and what's wrong. For example, while these athletes have to make their grades to play, it's their responsibility (just like any other student) to get a tutor from the university to help them and put in the work to get into better standing and attend their classes.
Like on that note, they can't - say - have someone hired by the school to wake up the athletes each day and make sure they get to their classes on time. Some of this can kinda spill more into personally responsibility. I think they make team rules about curfews when they're out of town for games, but I don't think a coach can - within reasonable power - make rules about how late a college football player can and can't stay out during an offseason or say what's allowed for all year round. He can advise and the school can discipline, but they can't be parents to these kids
Well the biology teacher is actually effected by how the class does (so a student missing/failing a class does influence it), however he works with such a larger base that the actions of a few students failing is usually balanced out by those that attend and do well.
I do see the dilemma you're saying here though, as a coach, unlike a professor - and having a smaller sized basis of success, has a career defined by a relatively smaller scale to judge success. However at the same time, if his only job is to coach a team, I'm not sure he can fairly be given powers that seem like they'd be reserved for deans or administrative offices (if they're allowed to have those). It might all just fall under a category of one of the hazards of the job you realize when you take it.