Social media reaches a very large audience. Promoting the platform on social media is really the right thing to do from a marketing point of view. The audience on btctalk is specific and small, I think the casino can afford to invest a small portion of their resources in forum marketing.
It’s true that Bitcointalk is small community compared to social media but the quality of member interaction here is organic than social media since post here is strictly moderated to assure that the content quality in every post of member here is following the forum standards. Yes the people on social media is vast but most of them is just talking bullshit and no sense at all. Atleast here, Casino that running there promotion can guarantee that all members that using there signature code will surely visit the casino or become curious on what’s the casino being offered.
Most of impression on social media ads is fake because they have bots to to trick the results of ads just to bring a good result.