You can stop doing drugs, but the drugs wont stop affecting you. Much like how tobacco users end up with long lasting side effects, other drugs have similar results.
That's just bad science, plain and simple. Tobacco, Alcohol, Marijuana, etc don't make you "former husks of yourself" decades after you've stopped using them, at least not in the way that you mean. Sure, tobacco causes cancer and alcohol damages the liver but cancer or liver diseases don't make you a "living husk of your former self." That's all in the psychology. They
can have lasting psychological effects, but that is more than treatable with both psychiatric help and counseling. What evidence do you have to suggest that it is never, ever worth it to give these people the mental health help that they need to get better?