I've used a YubiKey for 2FA for a year or so now. It just sits in my USB port and it feels too convenient - steal my laptop and you get my key. At least my phone has a PIN.
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.
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).