I've been trying to figure out why. Part of it is the desire to create and achieve. There is nothing more satisfying to some people than seeing a need, having an idea how to satisfy that need, and building a successful company around that need. Well, for one thing, if you can't do it here, you can't do it anywhere. The whole valley is organized to support the process.
Angels abound as sources of seed money and wisdom.
There is easy access to venture capitalists and the money and sanity they bring to the process. Law firms can crank out the pile of documents needed to launch a new corporation in a matter of hours. Benefits, office administration, finance, IT, and manufacturing can all be easily outsourced to highly experienced people. Highly qualified engineers are in abundance compared to anywhere else in the world, although the competition for their services can be intense. And, of course, Acuitive is there to help with market and product strategies and related functions.