Bitcointalk forum contains varieties of sub boards which means each related topic for discussion is channeled at the section it belongs. So when you see a gambling topic being discussed here, not that it is a major fact of discussion on the forum here. It is you who probably visited the gambling section where is designed specifically for gambling discussions.
However, technology is going on advancement and Crypto casinos has also been one trends in the online gambling sites.
So they runs a marketing advertisement here in the forum since the forum is sponsored by bitcoin and other cryptocurrencies.