Numerous reasons. We’ve stupidly decided there’s no need to confine them and get them proper care. We’ve stupidly decided that heavy policing and mass incarceration is an effective strategy, but is actually just ruining the lives of many over even the pettiest of shit. We’ve stupidly decided that intricate zoning and building codes and doing whatever we can to ramp up property values and taxes is a great way to maintain safety and stability and increase wealth within a community, but they won’t acknowledge that this is a major contributor of the lack of affordable housing. The US offers no significant resources in helping those in need. Hell, most of us are one bad day away from losing everything we have, and a lot don’t even realize it.