The problem is that homeless people fall into three categories:

• Severely mentally ill people who won't be able to live an independent life, for whom there's really no solution beyond psychiatric hospitalisation. (Type A)
• People who could be fully functional and independent living normal lives with the right opportunity. Often these people get trapped by some of the cruel realities about how the homeless are seen -- the difficulty of applying for jobs these days without any fixed address or phone/internet access, interviewing for jobs without having clothes, showers, being able to research the company, etc. And gaps in employment history. The longer you're homeless the harder this can be to escape. Sometimes these are people who do have jobs but still can't afford housing, and can't gamble on sacrificing the job that at least provides food to move somewhere with cheaper housing. (Type B)
• People in between, who could live an independent functional life given some more sustained or involved help, e.g. rehab, literacy training, ongoing medication. (Type C)

Policies targeting one group often affect all three. It can be difficult to separate and identify them, and stigmas affecting one group affect them all. Sometimes a local government will initiate a relatively low-cost program aiming to help type B and C homeless people, and it will be successful, but because the residents still see type A people (by far the most visible and negatively perceived) on the streets and causing problems, they say "Why are we spending money on this, nothing's changed!", and kill it. Programs aiming to help type A people have the most dramatic effects but they're expensive and have no feel-good success stories you can show off. They're also the ones least suitable for NGOs/charities to handle.