I wouldn't say all, because there are legitimate uses for creating and using mobile hot wallets for small amounts of funds. But yeah, anything holding serious amounts of money should be a hardware wallet or permanently airgapped. However, we both know full well that the majority of users don't do this. Hell, it's hard enough to get people to stop using absolutely trash wallets like blockchain.com or Trust wallet, let alone use an airgapped device.

So you adapt your storage based on your location. If you are concerned about something like water, fire, or pests, then regardless of if your seed phrase is on paper or in a book then it is at risk. A piece of paper I can put inside a small fireproof and waterproof container and still hide far more easily than I can do so with a book.