I see very few hydrogen cars (Toyotas), so I think it's safe to say that they are not very popular. I do see every fifth vehicle is a Tesla.
The main reason many still live here is prop 13, which severely limits property tax rate increases.
For example: My Dad's house in Conn. was purchased for $130,000 in mid to late 80s. It sold in 2019 for $230,000.
Many houses in southern California of equal size and age sold for close to the same (maybe $20,000 more) yet were worth $600,000+ in 2019. Original owner houses worth $1.5 million have property taxes of about the same as that $230,000 house. (approximately $4000/year).
So if you are an original owner or a second owner who purchased a house many years ago, you are wise to remain in the state, since the cost of living can actually less than in some other states. Some folks in Florida are seeing rapidly escalating property and auto insurance costs. Both are very reasonable here in many southern California cities.