Not there now but lived there over 30 years, 1963-1994. Back then it was a nice place with a lot going for it. Close to the beach, close to the mountains, close to the desert to go out and shoot up the place. Now there is no way in heck I could live there if for no other reason my guns would make me a felon. It is too bad that it went down the toilet like it has but I see no way it will change in my lifetime.
This is a big part of it. I live exactly one hour from the beach, 30 min from the mountains, 45 min from the desert (shooting, off roading, dirt bikes), and about 2.5 hours from the world's best sand dunes.
The simple answer is because it is not feasible to quit a job, sell a house and completely uproot one's life.
Bingo. Mix in small children and it makes no sense. At this point i stay because my kids have built life long friends and its not fair to yank them out because of liberal politics.
Truth is, aside from the politics, if you can afford to live in an upper-middle class neighborhood, you have nothing to worry about. Most of the bitching is "louder" on the internet. Ca is still a great place to live overall.
All that said, i'll move when i retire to either New Mexico, Arizona, Utah, or Texas. You can bet on that.