One theory: The Bay Area has become seriously ageist.

Many people have a hard time accepting working for someone a generation younger than them, and especially hiring a subordinate a generation older than them. The people reviewing your resume and interviewing you won't say it (they're not allowed to by law) but they'll definitely be thinking it, and it ends up being a huge waste of your time.

I genuinely think it's a locale thing. I've found work outside the area to be as high-paying and fulfilling, but without the casting couch feel to the interviewing process. In particular, look to large, legacy established companies trying to stay relevant. Many of them recognize the value of experience and pay accordingly.