I don't know how it is in the USA, but here they don't like to keep people in hospital if they are not a real threat to themselves or others.

When I was in the hospital after ODing the nurses told me that it costs a LOT of money to keep me there. Once my 72 hours was over, they let me out pronto because I really wasn't a threat to myself. They even let me have an overnight pass because I was getting anxious in the hospital.

There is no reason to hold someone in a hospital if they are not a threat to themselves or others. It's not about punishment, it's about helping the person.