As with so many, many things it goes back to Ronald Reagan.

Reagan closed long term mental health facilities in California when he was governor. The homeless population exploded, because many of the former patients couldn’t handle keeping a job or a home. This gave Reagan the ‘duty’ to hire more cops to handle the problem.

It worked so well in California he made it a national policy as soon as he was inaugurated.

You have many mental patient/homeless folks who end up in the emergency room several times a week. It costs more to keep them unhoused than it would to give them a long term place to stay.