Most sites, at least dice sites, provide either a login url (Just-Dice, SatoshiDice) or ask for a user name and password (BitDice, PrimeDice).
One of the benefits of Bitcoin gambling is betting anonymously.
There has been a couple of sites however that allowed you to login with your social media profiles, though they seem to be dead now

Do you think sites should offer the option of login via social media profile as well as the normal username/password?
For me it's a no because we all know that some sites or gambling sites are not legit or they didn't even give you some money they just get all of your money and worst your information too in order to blacmailed you to use it in bad way. So be careful guys. Many sites are not reliable and I told you I am one of th victim of those sites.