they let you drink/smoke/party, dont make you pay for anything, provide you with a car which means they pay insurance too, and they dont beat you....

They are likely afraid of you growing up and being gone. Why else would they have no reason to make you stay home when they've already speant time with you that day, and they dont really have problems with you partying? They pribably just want the security of you being in their house all night and them knowing where you are and what your doing.

Get a cell phone. That might help.