They get free services in San Francisco that they wouldn't in other cities. Also, many of the folks on the street during the day are actually housed, in public housing, and leave to do drugs since they will loose their housing if they do drugs at home.

Oh, they do move to another city. They move from homelessness in their original town, to homelessness in San Francisco, often with transportation paid for by their origin city/state's government, because SF has extremely lax drug and vagrancy enforcement, a mild climate, and easy access.

People who tend to think like you, who can plan in advance, are willing to get a regular job, don't do drugs etc, rarely end up homeless, even in the US. Most of the visible homeless on the streets of large US cities are deeply dysfunctional people, and lower rents or public housing won't make them more functional. Getting them out of public sight would be improvement for the public, to be sure, but the policies of the US cities ran by liberals tend to be extremely ineffective with respect to getting them out of public sight.

> But I wonder why homeless people don't move to another city.

Because there are few cities in the country that are as accommodating to the homeless as SF. And I'm not talking about weather, I'm talking about services, aid, lack of police harassment, etc.

If you're homeless it's certainly the best place in the country to live.