> What would I gain from using a passkey?

The correct question is What did others gain?

- Phishing free press fingerprint or faceID or Windows Hello for login into many important sites

- many people don't have time to type password, then otp. If most of the world did that then this would not be needed.

- And finally, YOU are not OBLIGED to use it. Let the rest of population use it.

- It is like SOME pay with phone/NFC-Watch etc. MANY still use card or cash...

> And finally, YOU are not OBLIGED to use it. Let the rest of population use it.

They are.