I think the (relatively) small overlap between knowing your password and stealing your computer is important here.

Passwords are weak vs. many types of hacks, U2F is strong. And vice-versa (easy to steal the Yubi-key + computer, but they still need the password).

Mine is on my keychain, plus you need my username, password and yubikey to authenticate, so if someone steals my laptop (oh noes!) they still have hurdles to jump.

U2F is protection against someone phishing/stealing your credentials online. Your password is your protection against someone stealing your laptop. The likelihood that a person who steals your laptop also managed to phish/steal your credentials is minute.

I use it for my email, and have set it up with yubikey + password, given that you need both it's not like you can brute-force the login anyways