Some (many? most?) of these kids are homeless by choice, it's a subculture as much as circumstance. They flock to the Bay Area (Berkeley/Oakland, and the Haight area) to be a part of the scene.
From an article in Hoodline, quoting Mary Howe, founder of the Homeless Youth Alliance,
> [San Francisco's Haight Street] is an international destination for youth who come seeking refuge from abusive families, alienating foster care and group home situations, and juvenile justice system involvement. These homeless young people encounter constant threats to both their physical and mental health while on the streets.
https://hoodline.com/2015/03/getting-to-know-haight-street-k...
Regardless you’re right it’s not a simple dichotomy. Similar to how if you’re living in a new Airstream, chances are you aren’t the same sort of homeless as someone in a runned down camper with little cash flow or savings.