That's not the problem. Private insurance does not offer flood insurance because A) it tends to all be due at the same time requiring a very large fund. B) It also promotes people living in flood prone areas. C) It's very hard to asses risks. Combined and you end up with bankrupt insurance companies.
The industry also feels B makes selling flood insurance a bad idea. That said, there are Private policies you can buy in some areas.
PS: Insurance companies like frequent small scale random events like car accidents, because they are easy to plan for.
I don't think point B is valid. Following your reasoning, the industry would also think that health insurances are a bad idea because they would promote an unhealthy livestyle.
The company would have to be huge to pull it off. One event like what happened in Houston could easily wipe out a big chunk of any fund they could amass. That kind of diversity could also be a problem if there are shared waterways, think back to the Mississippi/Missouri flood from 1993. I'm seeing 15 billion as the damages there, which is a large percentage of the "cash" pile Apple is claimed to have.
I believe it's a reference to the fact that even large companies, Apple is $800b, don't have all that cash on hand. To convert $15b into cash takes time. Disaster victims can't exactly pay for hotels or buy foods with bonds or stock certificates.
The industry also feels B makes selling flood insurance a bad idea. That said, there are Private policies you can buy in some areas.
PS: Insurance companies like frequent small scale random events like car accidents, because they are easy to plan for.