Possibly you misunderstood my point here. I do not doubt the fact that one can not store their keys in the above places you have mentioned. And as a matter of fact, these storage systems you have mentioned are prone to hacking at any point in time, and if that happens, the assets are gone because anyone who tries gaining access to accounts holding keys to wallets with assets automatically can be able to do away with the assets.

Now, my point is, as you have quoted, as a wallet holder, you can freely save your keys wherever that is safe for you to do so as long as it can not be easily compromised by anybody, and besides, you, as the owner of the wallet is free to make the choice of storage you deem fit to store your assets.