Depends on who is paying your bills and where you're living. I would wager that many on this board who have grown kids had the same rules.
Uh... well, family rules may mean an 18 year old has no money from mommy or daddy or no place to live, but it sure doesn't mean an 18 year old can't do whatever the hell he/she wants.
Bizarre that the NCAA requires a parent signature. Just bizarre.
I'm surprised that it has not happened already but it is only a matter of time before a highly rated recruit makes a stir on this topic. With all the minefields and ticky-tack legal proceedings you see anymore I can see a situation where a player wants out of a program and claims that since he is an adult the contract is void because of his parents' signatures blah, blah, blah. If he or she is under 18 I get it, as per the law, 17 might as well be 7 in most cases. But once you are 18 how can the parent be required? What if they are an emancipated minor? I am sure those smarter than me have already addressed this in the fine print of the LOI. Considering I have never seen one up close, let alone signed one to play college sports I am left to guess.