Solution: let silicon valley build more housing.
Also, it will let entrepreneurs and startups live on ramen noodles more.
Check out Tokyo (the largest suburban parts) for what the valley could look like with a bit more density; there still wouldn't be that many high rises. Tokyo also has a bit more fresh water to work with.
One important reason is the lack of core infrastructure like a centrally planned transit system. The thing to remember about the bay area is that it's not one city like NYC. It's a number of smaller cities and counties each with their own local governments, rules and constituencies. See San Mateo and other counties opting out of BART. Another example are various communities with maximum density regulations.
This is the kind of thing where you need a strong central hand to force these issues if you want your community to scale, but it's not clear that any local community would cede that power.