Social login doesn't necessarily give up that much info. Your social network knows who logged in to. The third-party only gets whatever info you accede to which usually is just an email address or name.
The huge bonus to users and site owners is that that site isn't storing a password for you. It's easy to screw up password storage.
Mind you, products would have to adopt it. But from a sec + privacy perspective it makes sense to have a 3rd party whose biz model isn't to harvest your personal details.
It's mostly dead now. People wanted the convenience of FB/GOOG/TWIT over the freedom of self-hosting.
God knows we need something. It's not safe "outside."
Looking through some of my Facebook apps: Headspace, Stack Exchange, and Netflix only have my email address. Venmo is an example that asks for my friend list because they want to use it for social features.
This is absolutely false. FB delivers a whole profile.
This is not exactly worse than web sites that allow you to sign up with an email address and request password resets: if your email address is compromised, then so are all your accounts. Actually, this situation is a bit worse, because there's also the chance that the user will choose the same password as they use with their email address or other accounts, so if the site they're logging into gets compromised, then their other accounts and email may be able to be compromised too.
With password managers being essentially mandatory now, it's not too hard to create a new email/password based account for every new site.
But recently I realized that I don't use my FB for anything. I have zero friends, don't allow friend requests and am unsearchable AFAIK. So now I am going to start using that account for social login, that way I don't have to bother with email/password.