I forget: What do we know about his parents? Did we actually ever see them?
In season 1 he shows up at their house and tries to move back in, they carefully debate about laying down the law and not letting them exploit their emotions, then throw him out because they found a joint his younger brother was hiding and blamed him.
In season 2, they try to throw him out of his house, and he blackmails them into selling it to him for about half of what they could have gotten.
The take away I get from those episodes is that their failure with him occupies their every thought and they are tortured by his criminal druggie behavior, but they've been through the wringer with giving him more and more chances and being disappointed they can't bear to face it again. So what they want and think is best for him is to really hit rock bottom and have to really learn to take responsibility. And I don't think, until they have closure, they will ever be emotionally able to completely put him behind them.