Could be true, but if they spend (?) money on research and see that their ads in other websites give them significant revenue increase, perhaps they find bitcointalk space less effective.
It is less effective than other modern platforms in marketing but there is fact that no communities are the same and companies can find different potential customer targets for their companies by doing marketing in different communities.
Like Twitter and Facebook can be more or less common in a nation so if a company has to choose either Facebook or Twitter (now X) for their marketing, they have to do local research on which platform is most popularly used in that country.
I think I am not biased to say gambling sites actually get good traffics and effects from their signature campaigns here, that gave them convincing results to continue their campaigns a long time. I see that no all gambling sites can run long lasting campaigns and it reveals that you are a Bitcoin-based product company or a gambling company, if you can not have good revenue from marketing, you have to stop it.