Peachy - Many people who become alcoholics or drug users choose that route to help them mentally cope with everyday life.
For example, 1 alcoholic I know who gets DLA. He does not have a recognised mental health diagnosis. But he is very fragile emotionally. Small everyday problems make him very depressed and anxious and to cope he reaches for the bottle. Of course this doesn't help in the long run, but in the very short term it does.
His fragile state emotionally and general inability to cope means that without support he won't do everyday things e.g. visit the Dr, shop in a supermarket, open and deal with mail, etc.
It is very difficult to know how much of his difficulties are caused by general anxiety and how much are caused by long term alcohol abuse. But he genuinely does need help to maintain a tenancy, deal with his finances, eat properly, go to the Dr, etc. I think there do need to be services for people like him - and there have been but they have been largely cut.
What people like him don't need is more money. Because fairly obviously he doesn't use the money to buy in support in whatever form, instead he uses it to buy more drink. And so he doesn't eat much, gets evicted periodically, gets into debt, etc.