Maybe you are thinking of very restricted cases ?
Many people i know along the Texas gulf coast have it if they are in an X or higher risk flood zone. Mortgage companies can require federal flood insurance before underwriting the mortgage.
If a structure is flooded a third time , there are limited funds available to elevate and repair existing or build new elevated structure or buy out the owner. There are many in Houston that have been through the process.
private insurance is also available but almost no one uses it due to cost.
Some coastal areas , such as near a beachfront , may be uninsurable due to storm driven waves and rising water. But other than that, the federal flood insurance program is chugging along. Premiums are rising though due to recent losses.