I'd think that 11% of CA homeowners is large enough that you have already hit the economies of scale and the price is largely a factor of risk. Quintupling that number is not going to reduce the price.
The number won't quintuple unless the price is reduced. Of course if 89% of the people were cheerfully willing to pay what the 11% are paying, then the price wouldn't change. And in that imaginary world, 89% would be covered.
The question is why don't the insurance people work a bit harder to broaden the coverage; they could make more money even at a lower price point.
Perhaps, those who are not covered are too resistant; they are not willing to get the coverage even at a reasonable price because of the way they perceive the risk/benefit. So that is to say, maybe it's a "hard sell".
