California, or at least it's major population centers, have been leading forces in global culture and technology for a couple generations. For some people that brings an incomparable value. For others, not so much.
But what I miss most are not the urban areas (where I lived most of my life), but the countless gorgeous destinations outside of the cities. I know I'm biased, but I can't think of many other places in the world that have as much to offer within a couple hours drive (that's for both LA and the Bay Area, among other metros).