I'm confused by this comment. The entire Bay Area is closed to SF. No single city there is not close to it, and people commute from the entire Bay Area to SF. Not everyone commutes there of course, but traffic patterns primarily cause traffic towards that city in the morning and away in the afternoon.

Each other city in the Bay Area also have their own jobs and individual traffic patterns of course, but housing prices are expensive in the entire Bay Area, often increasing as you get closer to SF but also to other city centers. The cost of living in the entire Bay Area is prohibitively expensive to most people, with people often needing to compromise between proximity to work, the size/quality of their home/neighborhood, having roommates to help pay (I have friends who have roomed in groups of 4 to cover rent), etc. SF isn't the only expensive city in that area.