Which sort of presumes that there are other places said people can shuffle off to. Their occupation of public parks is largely due to not having a designated place to go, or enough shelter beds, or a myriad of other problems.

One who has no home has fewer options on where to plop with all their things.

Individually, one could analyze each situation, collectively and systemically speaking, you will ALWAYS have homeless people when there is no housing safety net. there are a myriad of things can can occur in individual lives.

Homeless tourism is something that should be worked out between the desirable locations and the locations of origin that likely kick the responsibility can down the road in running homeless OUT of town, and hence to SF or wherever.

Honolulu and beach bummmery is something I've no knowledge of. Actual homelessness is something that doesn't occur much anywhere else I've seen in the world to the same level as it does in USA. I suppose that many places have folks migrating to the city from countryside regions in the hopes of a job and potentially falling on their face. I'm not sure where those folks are in many nations that I've seen (about 50, mostly Europe, South America, Asia, and North America)