Trying to imagine your grandmother setting it up herself to be able to log in to her Facebook is another matter, and why these things have never worked for the general public.
At home Yubikey is probably synonymous to FIDO not PIV/PKI. No whipping up a new one if you lose it. You better have 3 of them enrolled at any time, and have at least one stored off site.
I agree it requires significantly more work when you can't just call the locksmith for a new one -- IT -- if you lose one on your personal account you can only go get the spare key hidden under the doormat, a printed code in your safe, or lose the account.
For personal use, that equation is wildly different. Google isn't going to let you attach a brand new key, you've just lost your account forever because it rained.
Most services won't even need a second layer of auth, if someone steals your wallet - do they really care about your reddit account?
Generally, unless you are targeted by someone with a sim swap, it is good enough. Most people won't be targeted, but do have a good chance of something going wrong that makes them lose their MFA key.