All my evidence is anecdotal of course, but in 20+ years of working in the Bay Area, I've asked maybe 30-40 people who live in SF and commute, why the do so. Most of them were young single people (or young couples) and enjoyed the cultural aspects. They were happy to endure long commutes (often on company shuttles) just so they could enjoy those things on nights and weekends.

When I worked in SF, one left the city when they had kids, and one bought a house, but they just enjoyed urban living, being able to walk places, have lots of services nearby, etc.

A few were part of a family where their kids were born there and were in school there, or the grandparents were nearby.