Yes. A choice based on the fact that it’s an extremely nice place to live. I have never met or heard of a person who said “I’d like to leave but I don’t want the state of California to lose out on my tax dollars”.
They could easily save a bundle of taxes by moving somewhere else, or at least moving their money.
Some lower-tax (lower than California) destinations are incredible places to live as well - it’s not a choice between anarcho-capitalism and California.
So there’s at least a tiny bit of generosity there.
I do not think “generosity” of any sort plays in here. They’re not considering leaving for personal reasons but deciding to stay to provide tax dollars to the state. They’re staying because they want to. They like it here, or it works well for their business to be here. I don’t see any reason to believe that generosity plays in to it. California, despite high taxes, is simply a nice place to live.