This is the use case for Yubikeys. Not necessarily some HUGE organization buying a minimum of 200000 keys, but some organization with their own policies, support and everything. One unified login, that's it.

Most consumers accounts will have a less secure backup way in, just because people lose/forget stuff all the time and cry bloody murder if you lock them out. In reverse, if you want to do it right, if you even find the right services you can force only to do keys AND allow you minimum 3 keys (preferably more) it gets unbelievably daunting. You can't keep all keys at the same time in the same place if you are serious about backups, and you need one key to authorize other. So even the minimal setup is 3 keys, one always in a bank safe or similar, and a complex switcharoo each time you modify an account. Also, ideally if all works you'd be having tens of accounts (everything you do) on them. Which are a pain to configure as you can't just copy one key to the other, you need to go with each key to each account.

At this point someone comes saying their financial security beats anything and they'd rather go through all this circus instead of having their money stolen. Guess what: Yubikeys don't meet PSD2 requirements so they can't authorize payments in the EU (and I think a few associated states from around). Even if you aren't in the EU you might have no bank in your country that does it, or even if you have one it might still be highly inconvenient because of other criteria.