I think that's true for a demographic - the San Francisco 24-35 demographic (especially those in the tech sphere of influence), but I don't think it's generally true across the bay area. People who tend to think like this tend to be transplants that do not know very many people over 40, they don't know anybody from, say, Redwood City, Hayward, or Albany or even the Sunset district. I say this as a transplant under the age of 40, but the majority of my coworkers are much older despite most of them also being transplants.