What prevents passkey being used alongside password (+ email 2fa)?

> Maybe I am getting old but password+yubikey/webauthn was really top UX.

It most definitely isn't. Any 2nd factor that is not the device I am currently using (either a yubikey or my phone) has a non-zero chance of not being near me when I need it, leading to the constant question of "where the fuck did I put that darn thing", only to find out that the cat has decided to believe the yubikey is a mouse and tried to devour it, the phone's battery went dead...