Last winter’s atmospheric rivers did $4.6 billion in damages and wrecked thousands of homes, most of them without flood insurance. But in the months after, people didn’t sign up en masse for new policies. About 3,000 Californians enrolled in the National Flood Insurance Program, which insures the vast majority of homes in the state, between last January and July, but over the past few months enrollment dropped back down, from 194,625 policies to 191,622 policies in December.

“We haven’t seen a rush of people on this end saying, ‘Oh, I’m gonna get flood insurance, I need flood insurance, I want to buy flood insurance,’” said Rob Bhatt, an insurance analyst for LendingTree. “That’s a little surprising.”

So why aren’t Californians insuring themselves against floods?

There are a few reasons.

For one, they’re not required to. Unlike fire insurance, which is required for any federally backed mortgage in the state, flood insurance in California is purchased separately from homeowners insurance and is only required for land that FEMA estimates will flood more than once every 100 years.

And those maps are out of date: While independent risk modeling has found that 23 percent of California properties are in high flood risk areas, less than 2 percent have the required insurance.

NFIP policies can also be expensive, especially on top of rising regular homeowners insurance prices, which are going up to cover increased fire risk. An average policy is about $866 annually, or $70 per month, Bhatt said.

“If you look at the combined cost of insuring your home, including your normal homeowners insurance that covers your fire, that part of insuring your home has gone up so much that at that point you’re saying ‘Oh my gosh, I’m already paying so much for my regular homeowners insurance. Why am I paying for flood insurance?’” he said.

There’s also the risk perception. Property owners may be numbed out to the drumbeat of other natural disasters like drought and wildfire to the point where they overlook the opposite threat.

“I think the biggest problem for flood insurance in California has been the 20 previous years where the only problem we talked about was drought,” said Rob Moore, director of flooding solutions at the Natural Resources Defense Council. “Then the next problem we talked about over the last five years was fire. It’s only been the last year that floods came back into people’s consciousness.”

Private insurers have been slowly increasing their flood policy-writing over the past decade, especially in other flood-prone areas like Florida and Puerto Rico, but they haven’t made a significant dent in the numbers of underinsured residents in California, according to Nancy Watkins, a consultant with actuarial consultant Milliman.

“Companies who are struggling to get their rates adequate for a tricky peril like wildfire that they are already insuring are less likely to go into a new peril like flood,” she said.