Because they have Hollywood and Silicon Valley (AKA Apple, HP, tons of high tech companies), and tourism since California is very nice and beautiful. But the problem is that their taxes are ridiculous, and a lot of companies as well as people are moving out to states like Texas where taxes are low, life is cheaper in general, and pretty much everything is cheaper. I've been to California, and it's like paradise, until you find out how expensive it is to live there and how greedy those politicians want your money.
.. which probably means taxes that would be considered extremely lenient in Europe or anywhere else. Well, even your far left is still right wing...