This is probably because they mostly use cryptocurrencies (including Bitcoin) as their primary payment methods, this forum is related to cryptocurrencies, and they know they are going to find people with a general interest in cryptocurrencies who might also like gambling. I don't see any other logical explanation for this question. A casino accepting Bitcoin as a payment method would look for gamblers having Bitcoin or at least have an interest in cryptocurrencies which makes them potential customers.

Have you heard about targeted advertising? It's basically the same thing. Casinos advertised on this forum accept cryptocurrencies, so they are targeting people who are interested in cryptocurrencies, and I can't think of a better place for any company to find such people than this forum.


You answered this question yourself: