Because we're taught that cruelty to the homeless person is a deeply apotropaic act + protection against ending up like them. And bc we get off on viewing the powerless with scorn. We like to forget that homelessness CAUSES drug addiction. And that it's far harder to get off the street than onto it.
The US likes pretending that the numbers haven't shown how giving the unhoused a permanent address, helping them get their documents back in order to they can maybe get hired, and where needed, getting them mental health/addiction care, is MUCH cheaper and more effective than continuing as we are.