In a four-year residential college, many of the students living in dorms, especially those fully subsidized by their parents, are not adults by several of the criteria you mentioned, yet colleges make little effort to regulate their behavior, and it is impossible for parents to do so. I don't think there should be a supervision "cliff" at the time students enter college. What the slope should look like is hard to say.
And failure to appropriately navigate this cliff causes what I like to describe as Catastrophic Permanent Life Failure.
I still have nightmares about college on a regular basis.
I agree with Bostonian's point here.
