That’s a really important point. It’s true that self-hosting your bitcoin comes with the responsibility of keeping your seed phrase safe. I think it’s crucial to have multiple backups in different locations, and even consider storing a copy in a safety deposit box or with a trusted friend or family member. It's also good to use a hardware wallet for extra security.
You are right, everything in this life comes with consequences despite its advantage. In a natural disaster like this where lives and properties are been lost, one cannot be sure if their seed phrases will survive them because no one can control such disasters. In some disasters like earthquakes, fire outbreaks, and floods, no matter how safe you keep your private key or seed phrase, you might lose them because you will never care about them at that moment. Cramming seed phrase is not a bad idea rather because their are people with good retentive memories, I think only such people can survive with their Bitcoin if they can remember their seed phrases.
Nevertheless, that shouldn’t make leaving our coins in centralized exchanges safe and reliable because the exchange can easily get hacked and to get refund will be a problem, and your privacy matters a lot which you are not guaranteed of its safety with exchanges.