Both Android[1] and iOS[2] have both recently gained support for acting as WebAuthn authenticators, supporting authenticating on other devices (Chrome/Safari on desktop gives you a QR code to scan, then the devices communicate via Bluetooth to use the phone as a WebAuthn authenticator). The keys also sync via your Apple ID/Google account. Should go someway towards making WebAuthn a viable replacement to TOTP for people who need to sign in across multiple devices and don't want to buy a hardware authenticator, though more widespread support is necessary I think.
Sure, don't then. But other people are insistent that they can't tolerate the inconvenience of needing to own more than one authenticator, and yet they also can't tolerate the risk of losing an authenticator, so this is how they can square that circle.
My point was more that WebAuthn is starting to become a more viable option for the average person, with phone based authenticators that can be used to authenticate on multiple devices and keeps your keys backed up. I wouldn't use Google sync for WebAuthn myself either.
[1]: https://developers.google.com/identity/passkeys/use-cases#si...
[2]: https://support.apple.com/en-gb/guide/iphone/iphf538ea8d0/io...