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.
Yeah it seems some people dont understand the reasons for people to gamble with bitcoin, many of those that gamble with bitcoin do so in an attempt to remain anonymous, I have seen some traditional online casinos trying to accept bitcoin but then they will ask for all kind of details about who you are, so Im willing to bet that they do not get a lot of customers due to their policies.