Also, when the constant pressure is taken off and their basic needs are taken care of, maybe some of them can reflect and take a less forced decision to quit. But maybe I'm underestimating alcohol's hold.
That'd be an interesting thing to check out. They do get to see first-hand what it's doing to others around them, over a period of time. It'd be a unique incentive to quit.
I seem to recall a story about this place, or a similar one, where a couple residents decided to sober up after "living the dream" (free booze for life!) and still not finding happiness. Many more tho drank themselves to death there.