California, like pretty much all states, forces everyone who drives a car to "cover" it. That is, the state forces them to buy insurance.

Even – in some cases – if they don't drive it. There are states that require the owner of a garaged (or otherwise stored) car that isn't driven to be registered – and in most cases, in order get or renew that registration, the vehicle must "covered." This is revelatory as regards the nature of such "coverage" in that it shows the supposed justification for obliging people who own cars to buy "coverage" – i.e., that it is necessary in order to prevent innocent other people from holding the bag for the cost of injuries and property damage arising from someone else driving a car that isn't "covered"  to be just that; i.e., supposed.