The reason isn't because everybody wants a college degree, it's because having it in the job ad opens it up to H1 visa holders, which make up a significant part

The reason isn't because everybody wants a college degree, it's because having it in the job ad opens it up to H1 visa holders, which make up a significant part of the silicon valley workforce (not just from one country, there is a crazy international contingent in the SF Bay Area). Many companies have entire departments that are made up of an H1 workforce and will favor them in hiring - which is a little odd considering that you are supposed to pay over market rate for an H1, but we all know there are ways around that (either changing the job title to a lesser paying job, using a job title that has a below market rate for the same set of duties as another title, paying the "contracting company" the higher rate, but the actual worker gets paid less, etc.). I've seen a handful of companies actually require a degree, but almost all will waive the requirement based on experience - especially for someone who is the right fit. I've seen some (or some departments) that will only hire high profile school graduates, but that kind of a thing is usually specific to a particular market.