I agree about not wanting to be with a teenager. It is odd how we miss who they were, and yet know we cannot have them in our lives.
Having non contact is much easier, but occasionally we forget how awful they are, and start to remember them as they were. A reality check is then needed!
They are not our friends, friends care for their friends and treat them well. Perhaps they 'need' this reassurance that they really aren't that bad? I think that they lack the courage ad energy to put things right, if and when it dawns on them that all is not well with them and their strange new world. A few do, and even then it takes a huge amount of patience and encouragement from the lbs, who by that point may well have better things to do than deal with the uncertainty of a person who has been crazy, and may do it again . . .