My first observation which i want to bring to your notice is that the forum is not being abbreviated by BCT, i think most users do make use of BTT instead.
Secondly, here are some few reasons i think makes it look the way you have seen the forum to be having high posts from gambling sections.
1. The gambling platforms have the most signature campaigns on the forum and they ensure that at least their participants make posts on the section on a weekly base.
2. Also, considering the way gambling is being accepted and well played by people, making an advertisement for a platform on such section will help get the required attention needed for them to be recognized.
3. There are sections like the wall observer as well where daily posts being made there are worth a number of pages and could be the second after the gambling posts.