I was talking to a doctor friend today. She treats many alcoholics, drug addicts, and heavy-eating diabetics who come to the hospital regularly to be cleaned up - only to go right back to their self-destruction.
Medical ethics and the law mean that these very sick patients can't simply be turned away, even if they have been treated and taught better many times before.
This is a "moral hazard" problem - when we subsidize help for people's problems, some of them will produce more of that problem than they would if they were on their own. That is the hazard of helping. Yet it is a great moral good when the able help the hurting.
I do not think there is an excellent solution to this problem.
The best solution I can think of is that the persistently self-destructive can have the free or subsidized care that they get now - at the cost of losing some freedom to damage themselves. For example, after the nth detoxification for an alcoholic, they have to take Antabuse, either implanted (if such a thing exists) or show up at a location for to be observed and certified while taking it. Accepting the detoxification would legally constitute voluntary acceptance of this restriction for a time - say, a year.