The problem with your theories is that actual evidence says the programs work far better than anything else we've tried. (I don't intend that to be mean or glib

The problem with your theories is that actual evidence says the programs work far better than anything else we've tried. (I don't intend that to be mean or glib). These programs typically assign a caseworker who gets to know the homeless people and forms a relationship with them. The early period involves a lot of hand-holding and helping the homeless figure out (or re-discover) how to live a productive adult life. Most people who end up homeless turn to drugs, prostitution, and have any existing mental problems hugely exacerbated AFTER they become homeless. In other cases it is some other underlying situation (abusive childhood, etc) that triggers drug use that leads to homelessness. There's also a strong selection effect: many people who become homeless quickly attempt to find employment and a new place to live. Those who don't get out of being homeless quickly become unemployable and thus are locked into the cycle. As a society we seem to be stuck in this Victorian-era meme that moral failure brings calamity upon people (aka the Just World fallacy). That applies to success the same as failure... being ambitious and smart is a necessary but not sufficient condition to become successful. If Mark Zuckerberg got hit by a drunk driver (through no fault of his own) and became a paraplegic while at Harvard he wouldn't be a billionaire today. If he hadn't gotten into Harvard would he have had the connections to get funding and start Facebook? A million things entirely outside his control had to go right for him to be successful. It was a combination of his character, circumstances, and pure luck. If you don't have all three you won't be successful. Similarly it doesn't take much weakness or bad luck to completely ruin someone's life.