It's the result of a ballot measure in 1988 (Proposition 103). While it's kept premiums in CA 10% lower than the national average (much lower than they'd otherwise be), it's causing insurance providers to pull out. Another example of consumer protection that has unintended consequences. Either way, people are going to complain.
https://www.kpbs.org/news/local/2023/06/08/consumer-advocate-calls-out-insurance-commissioner-as-major-insurers-stop-selling-new-policies-in-california