Which casino has closed their ANN thread here on bitcointalk except for owl.games? I do not know what the reason for their decision may be but generally speaking, all the casinos which have their Ann thread here are active and none of them seems to leave this forum.
Why would they leave this forum when they are getting good business from here? a good casino should have a presence on all social media platforms, on all gambling related forums, and also be active on their support on their website. Leaving any marketing space unattended will mean less business and fewer players for that gambling site.
As long as I remember since there was a discussion on it, owl.games locked their thread and left the forum because there were some accusations against them from their players and they probably couldn't face them or clear the issues, so they decided to just stay out of the forum which has really made them look bad even if they aren't really bad.
They didn't say this specifically before locking their thread. The excuse was to focus more on the customer support on the website and do some necessary changes or things for the betterment of the platform, but the actual reason as debated earlier was actually that they were accused of scamming people.