When I first came to the Bay Area, it took me an inordinately amount of time to realize that the BART didn't go all the way around the Bay. I just assumed that it did because it's what made the most sense.
In fact, the county of San Mateo voted against BART because they didn't want people from other counties to come and take their jobs. So, because of this, you have a ridiculous patchwork and mishmash of transit "solutions" from various levels of government, none of them really working well. If you had a BART that went around the Bay, you could eliminate Caltrain completely, and move that money into making BART even better. Of course, those are at different levels of government, which means that you couldn't really do that.
It's at the point now where, except for people that take Caltrain during rush hour, and MUNI in SF, most public transit around the Bay is for poor people. Most people with higher paying jobs can't afford how slow public transit is, and it creates this negative feedback loop where they don't get enough funding to justify a better schedule, etc.
Yes, Google has a great bus system that is a competitive advantage when it comes to hiring people. But this is private transit, and it doesn't directly translate to public transit. If you have to service an area like the South Bay, you have to not only service the areas that people need, but then you have to deal with unions, costs, etc.