Facebook is too restrictive regards crypto content that they have become an unreliable platform to advertise. Instagram is more picture related platform and Tik-Tok video related, and although I'm not familiar with their policies, I think it's pretty possible to advertise gambling content there when adapting the ads to each platform style. On Instagram banners explaining promos could be displayed in abundance and at Tik-Tok short promotional videos could be made. About Bitcointalk specifically, it's more gambling oriented advertisement, because it's a crypto niche which also embraces a significant portion of gamblers' community. So we could say the traffic here is more valuable than the traffic at social medias and that might be the reason why casinos invest so much time and money at the forum.