>When you make housing for the homeless dependent on being sober and clean, just what, exactly, do you expect as an outcome if not that?
Note my use of the word "unmanaged". It's possible to house people with active substance abuse problems, but it's considerably more challenging, particularly heavy drinkers and crack users. There is a significant impact in terms of care because you're dealing with people who have a limited capacity to look after themselves, but the primary impediment is aggression and violence. It only takes one difficult resident to turn the whole facility into bedlam, at which point you're faced with few options other than evicting them for the sake of the other residents.
Wet houses do exist, but they're a lot more expensive to run and they face far more local opposition. They're a fundamentally good idea, but housing alcoholics and other difficult-to-house groups is a lot more complex than just "open more shelters". You need a highly skilled multidisciplinary team to make it work, and you're still going to have some amount of unavoidable rough sleeping.
If you still don't see where I'm coming from, imagine a crack addict with diagnosed antisocial personality disorder. Imagine someone who has been arrested multiple times for assaulting medical staff and police officers. Imagine someone whose life revolves around multi-day crack binges, which usually end in an episode of drug-induced psychosis and either an ER visit or an arrest. These people are not exceptional in the population of chronic rough sleepers, but they're exceptionally difficult to house.