If your phone is lost, how are you going to sync your passkeys to your new cheap android? In a passkey-only future, you cannot login to your Gmail account without your passkey, which is only on your phone, which you've now just lost.
What am I missing? Either we retain passwords as backup for a lost or stolen device - in which case, all the security concerns are still there - or we only use passkeys, in which case we've added a clear nonrecoverable point of failure in the system.
What confuses me is that for a long while we told people to not write their passwords on a sticky note, to not write them in plain text somewhere.
Then we introduce all these "security" mechanisms that make it literally impossible to recover an account without backup codes.
Where do you store the backup codes? The average person, if they store it at all, will store it on a plain text file or in a sticky note.
Except that this creates a much more brittle system. Systems are safe when they are routinely tested/used. If you routinely have to enter your password, you are aware you need it. If you don't need your password, and you never have to enter your backup codes, you won't feel the importance of them until you actually need them.
It's the whole "I have backups" vs. "the backups actually work" problem except it's pushed onto the users who have zero technical knowledge.
FWIW my break-the-glass actual use of backup codes is for access to my password manager.
Everything else which has ever given me a backup code... gets stored in a secure note in my password manager.
It is just another knowledge-based factor. It is one that they are reasonably sure you aren't spreading around the internet. It is one that the site gets to pick rather than the user. But in reality, they are a often just a way to try to reduce some support and identity verification costs.
The path to get to the password manager is the case where the backup codes truly matter, because without them there may not be a way for support to restore access. Those codes may be your only way of regaining the master encryption key.
But that also winds up being part of the trade-off of security vs user friendliness. Some password managers are way easier to get back into.