I big part missing from this conversation is what happens when you lose a device, want to leave an auth platform, or are deplatformed.

I don't want my credentials to be locked into any vendor, be it Apple, Google, or Proton. I currently use email + passwords + yubikeys. My credentials aren't dependent on some passkey auth server working correctly, or device that I don't control or have copies of. If Google or Apple wanted to ban me without recourse, in theory it wouldn't affect my ability to use other services. This doesn't appear to be the case with passkeys.