@Jeruba I think life on the streets is virtually inseparable from drug use. You use the drugs so you can bear the life that drug use has brought you to.
That is a sad misunderstanding I think most (and I am not going to bite my tongue on that because I have seen it 1st hand) people have, mainly because the drug attic or alcoholic homeless are more visible. There are homeless people who are homeless but still manage to hold down jobs. I won’t go into Christians and Believers who are also homeless and have no need for booze and dope. That I deal has been batted around so long and hard it is believable like the myth that every gal who is a stripper, prostitute or porn star was sexed up as a child.
To the OP question, every single day, I work with outreaches, congregations, and with the homeless blessing them with extra needed items I come across and trying to nudge them to better choices in their life if they are too stubborn to give God a try. I don’t know where you live, but sometimes a place can get more homeless depending on what outreach is available there for them. I have never seen a place where the homeless just flocked to, not even here where there is more outreach and congregations involved with it that if you are homeless you can have at least one hot meal a day if you know where to go.
The cause I see is manifold, it can come from losing one’s home and not being able to obtain another because there are not enough or no places within their income to get, not enough credit, with nearly every place that is not privately owned running background checks, some of those who have the money can’t rent because of their legal past. Not to mention who I can the ”functional mental cases”, they are not on the planet well enough to hold down an apartment, keep it clean, keep the lights on, buy food and cook it and more important, pay the rent on time. The cause is more than just one thing.