Nothing wrong with your answer itself, but having to be Apple or Google is a PITA. These account are ultra critical already and you will want maximum security to access them.

This means if you go on a trip somewhere you absolutely need two devices. If you kill your phone and want to buy another one ASAP, you wont be able to do anything with the new device until you can convince the platform it's you. With passkeys you're just SOL. Imagining if you needed a phone to get back from your trip - e.g. etickets, auth needed etc. - it becomes a nightmare scenario.

A third party manager makes it easier, but it's a lot less usable that the first party ones.

Reasonable people make different life choice, having to constantly think about backup strategies whenever I'm away from home would be so stress inducing to me.

>This means if you go on a trip somewhere you absolutely need two devices

If you want multi-device redundancy, you have to carry a second device of some type, it's hard to get around that. I almost always travel with an iPad in addition to my phone, so I have a second device.

In addition, my wife (who travels with me so if my iPhone is stolen, hers might be too) is one of my Apple account recovery contacts, plus I've set my sister as an addtional recovery contact, so even if I'm out of the country and I have to activate a new iPhone, I can call her to help with the recovery. So all I have to do is find an Apple store and buy a new phone.

I also carry a USB key tucked into my luggage with the recovery kit (encrypted) for 1Password so I can activate 1Password on any new device and have access to my passwords and whatever passkeys I don't have in iCloud.