There's a heavy need for rehabilitation shelters, but the public at large looks down on addicts and refuses to fund them. That leaves organizations like the Salvation Army to take up the slack, and the results can negligible. There's very little support on the private shelter's side other than providing a roof, a cot, and some basic directions to nearby organizations. Meanwhile the addict is meant to improve their behaviour almost immediately, fight the shelter itself to maintain their cot, and facilitate setting up their own recovery. Many of them choose to be homeless rather than put up with the ridiculous standards of these privately run shelters. Meanwhile on the public side it's a problem we started working on in the 1970s after the Vietnam War created a large wave of drug users, but Reagan gutted psychiatric care in the U.S. in 1982 and that meant that any progress towards making those shelters a reality was smashed into shards. What we were left with is people being put into psychiatric facilities that don't have the type of structure needed to rehabilitate an addict.

There's no way up from the bottom other than having another person take your hand. And nobody wants to be the one to reach down their hand. They rely on broken organizations and inappropriate tools to do that because their proximity to that ruin makes them uncomfortable. Either the addict gets screwed by the police or they get screwed by the rehabilitation facilities. So the addicts decide to turn away from both, and the public decides to turn away from the addicts. As you said, those in the public ostracize and shun them.