It is important to note that 99% of the world's internet users are not using the internet to learn about how to secure private keys.
They are not even important in this story, because here we are discussing additional ways to protect the accounts of the members of this forum. Each of them should know what a private key is, and how it can help them protect their BTT account.
Furthermore, there is no single 80% secure way to save private keys; they are lost over time due to accident, malware attacks, phishing attacks, and most of the time our gadget is stolen or broken down. Offline save is not safe, nor is online save, and because there is no 100% proven way to secure private keys, we will continue to post stories about lost private keys on the internet.
There are ways that are 99% safe, because nothing is 100%, and everything you listed can be avoided and prevented. Careless people keep losing their devices, becoming victims of malware and phishing, but do you think any additional protection would help them? From 2014 until today, I have not lost a single address, let alone a private key, nor have I been a victim of malware/phishing - and I am no expert in online security, but an average internet user who has learned some basic things that make me relatively safe when I am online.
I don't know about you, but I throw away my wallets every two years. Staked addresses help, but they are insufficient.
It's the first time I've heard of such a strategy, and I don't see the point in it. I keep everything related to Bitcoin no matter how unimportant it seems, because I never know if I will ever need it. It's not that I need a warehouse for that, everything fits on a regular USB stick that costs a few $.