The "why" to my mind, is levelling Let me explain, People are most comfortable when others they know and associate with are on the same level as them. And they will bring them down to accomplish it. The "mother" in your story sounds like that kind of person. Don't get me wrong, she may not even be doing it consciously. but she IS doing it. Taking the boys out and getting them wasted gives her a temporary feeling of being super cool and youthful and also serves to aid her delusion that she's doing nothing wrong. Inviting to do the same with your son is the same thing. I sure hope he doesn't go.