This is the crux of the issue in my mind. The tour buses are a symbol, not just of gentrification, but also of the failure to promote progress.
Wait, what? You're complaining that these companies don't promote public transport at the same time as complaining that they're already running bus services for their employees? Would you prefer those employees are all using cars? Do you think there is huge pent up demand for commuter bus routes from central SF into the bay area? If the buses were open to the public, either there would not be much additional actual demand beyond the tech industry (in which case nothing would change), or there would be a lot of additional public demand, in which case there'd have to be even more giant buses sitting at the bus stops.
Public transport in that part of the world is useless, but it's not useless because SF can't afford to invest. California is one of the worlds largest economies all by itself and SF is one of America's richest cities. Public transport there is useless because the entire layout of the region creates too little density for working transit, and any attempt to upgrade infrastructure or increase density runs into protests.
I know lots of Google employees would love to work in the SF office, but they can't because it's not big enough. Why is there not more office space in SF? Well, go see the comments above.
Here's another example - Google has been trying to build a bridge in a part of Mountain View for its buses for a long time. Surely this is the kind of investment you would like to see. Private corporations paying to build new roads to take some of the pressure off the 101. It got voted down. If Google can't even build a simple bridge in its own back yard, how do you expect these companies to re-build most of San Francisco? Surely that's the governments job anyway?