It's actually a LOT easier to explain to your grandma than a recent MFA app like Microsoft authenticator that requires a smartphone, the user to unlock it, choose the notification, to enter a code from a list and confirm with fingerprint.

With passkeys via yubikey it's insert key, enter pincode (just like at the atm), touch and go. You don't even have to enter your account name or email because that's derived automatically.

Anyone who can get cash out can use a yubikey. Very different for MFA apps.