Probably due to the extreme level of veto-ism in the Bay Area. Everyone wants internet, but if 5 people complaining about yards or roads being dug up can get work to stop indefinitely, costs are going through the roof. There's far more uncertainty in that political environment than anywhere else.

For reference, I live in a small town of ~6,000 people, and we're getting fiber laid. For the longest time we only had 25mbps, and then a new provider came in with coaxial and offered 200mbps (with a data cap), and now a third is laying fiber.

Our average income is $34k/year, so it's not because we have more money than the opulent Bay Area.

Google announced they would bring service to San Jose, along with about 20? other locations, and then later in the week, AT&T announced they would bring fiber to the listed communities in their ILEC territory and a couple more for good measure. And then a few months later, AT&T started rolling it out. Google hadn't figured out how to access poles or where they wanted equipment by the time AT&T was offering service, so they gave up. They did get some new service areas through aquisition, but I don't think they've announced any new construction service areas in a very long time now.