I think it may have a lot to do with how much pain people are willing to face to become self-aware and get better. It also may have to do with how many consequences people face before they choose to do something differently. Plenty of people were raised by active alcoholics and then become alcoholics themselves. They may stay in active alcoholism for a long time if they are fine with it and don’t face a lot of consequences. Same with narcissists or anyone else with a bad mental illness. Self-awareness and growth come with a lot of pain and a lot of courage, and not everyone is willing to do face that.