Comment by johnnyanmac

1. It's a network effect. If you're raised around doctors, go to school with prospective doctors, and your school gets many university recruits from a good doctor college, you will strive to be a doctor more likely than not. SV had a bunch of tech companies and falls into the same kind of environment.

2. It's probably a matter of Venture capitalists. Even if you aren't from SV, you may strive to go there to get funding for a pitch or find talent. Similar to your prospective actor that moves to Hollywood. Go where the crowds are.

Now, we can ponder why SV became a tech hub, but current market forces makes it ripe for tech startups.