Correct bitcointalk is at the top if we talk about numbers of crypto users but its also good to market outside since there are also crypto users who doesn't use bitcointalk at all, many of them stay on the platform mentioned by efialtis so if they do multiple campaigns on various platform well possibly they can hit the greater audience and bring them here to play.
Not only bitcointalk which is bigger there are indeed several platforms that can reach a bigger audience to bring the community to play on their site, so it's true that some don't know the bitcointalk forum even though we think of it here as the biggest and most successful marketing in gambling so every platform will definitely hold a campaign to attract attention with a lot of promotions, therefore they will enter all platforms to expand the campaign with many contests being held.