I use it when I’m on a desktop. For example instead of opening up a password manager and entering your password manually I would use LNauth and just scan a QR code with my LN wallet and boom I’m in. 

I don’t like it as the only way to sign in to anything but it is a convenient option when going from mobile to desktop 

I'm thinking about it but i've seen a lot of UX nightmares with lnauth, do people actually want and like lnauth login? Maybe if it's just a backup or recovery auth method?