I've known of several teams that actually had contracts. I believe that some others distribute a list of team rules and require all recipients to sign a sheet, indicating that they've received the info--comes to the same thing, I suppose.
With a contract, what the coach expects is completely clear. I could see how it might actually be a relief for the athlete, too--no wondering about "is this okay?"
______________________________________________________________________________________________________________________
Separate, but related, questions:
Do any teams forbid (or limit) drinking?
Do they set bedtime hours?
Do they forbid posting on discussion boards?