We've used social login since early 2015 and it's been a tremendous success for us. We occasionally have someone ask why we don't just let them set a username and password anymore. A few people don't have Facebook or LinkedIn accounts (it's okay because now we also support Google accounts!) and a couple others have wondered why they might want to grant us some access to their social data.
It all boils down to 3 things:
Customer Support - one of our top support requests was about password resets. Social Login has reduced those questions by 80%.
Customer Experience - you don't need to remember a new username/password and when creating a site for the first time, you can now import basic information about your group with just a single click of a button.
Security - this is actually the top reason for using Social Login. No more shared passwords, better fraud detection and much faster resolution of hacking attempts.
We wrote a detailed breakdown of this choice, why we made it and how it's affected the experience of customers like you and of our internal team. Check it out over on Medium.