Passkeys get synced between your devices so they aren't any more fragile than passwords in a password manager.
Passkeys _may_ be synced, but that isn't guaranteed. For example a "device bound passkey" isn't synced.
The big providers only want themselves to be able to backup passkeys. I do not want to handover my secrets to Apple/Microsoft/Google.
Passkeys _may_ be synced, but that isn't guaranteed. For example a "device bound passkey" isn't synced.