Doesn't make sense to make it mandatory to login using facebook or twitter in a gambling site. That sounds fishy to me. But if I badly want to try out a gambling site I might consider making up a fake twitter , google or even a facebook ID. Will never you my real one!
I think you're right, one reason why some of us preferred online betting was to protect our privacy and stay anonymous but if it do happens that we ought to login with our social media credentials who's going to use the real one? We'll make fake social media accounts for gambling.