The entire value proposition, and the reason big sites are pushing them, is they take the user out of the loop of authentication. You are no longer authenticating the user, you're authenticating the users device.
For websites you don't have to worry about cookie theft and dealing with the support load of users needing their accounts reset or dealing with fraud. You can also do some level of attestation to hardware which makes automated account creation more difficult.
For the user it offers no additional benefits. You still have something secret that gets presented to a website to login. Password managers solved this problem. But now for some reason you can't log in when you buy a new laptop.
The entire value proposition, and the reason big sites are pushing them, is they take the user out of the loop of authentication. You are no longer authenticating the user, you're authenticating the users device.
For websites you don't have to worry about cookie theft and dealing with the support load of users needing their accounts reset or dealing with fraud. You can also do some level of attestation to hardware which makes automated account creation more difficult.
For the user it offers no additional benefits. You still have something secret that gets presented to a website to login. Password managers solved this problem. But now for some reason you can't log in when you buy a new laptop.