I completely agree. The stipulation that "all major browsers" support U2F is totally arbitrary, since by definition anyone who purchases a U2F dongle is already making choices about what hardware and software to use to maximize his or her security. Ironically, U2F is especially useful for less sophisticated users, since typing in a 2FA code is potentially hazardous in a MiM situation, but plugging in a U2F device is at the very worst ineffective, never dangerous. And the least sophisticated users these days (I'm looking at you, parent/spouse) are likely to have cheap Chromebooks, which of course run Chrome.
Despite quite a few pending gift subscriptions, I have never managed to convince a non-technical person to start using LastPass, and a simple "just plug in your key" login process would go along way to helping me convince them.