It is not good to hold your coins on exchanges but hold them on a self-hosted wallet. This brings the responsibility of how not to lose your seed phrase because if you lose your seed phrase you will lose your coins.
If there is a natural disaster that flood your town or an earthquake that destroyed the building your seed phrases are, what are the other recovery means that you have in place for you not to lose your bitcoin?
We should backup the seed phrase in a way that no matter what happened, we should still be to have access to the seeds phrase. What are you approaches to make sure that no matter what happened, you will have access to your seed phrase if you are still alive and your brain is functioning properly.
I think you are going too far with this your imagination, how can you say about earthquake destroying the building that your seed phrase are. Moreover let's take for instance that if sometime like that occur did you think you will still be talking about your seed phrase? Is when you're still alive that you will think about your seed phrase. Though you may be right but your imagination shouldn't be in that aspect.