Interesting discussion. Want to add something from my perspective, but it was such tough Monday that my brain refuses to work. So, it won't be deep insight.
First of all, we should admit that now Bitcointalk isn't same as it was 5 years ago. Traffic and activity is declining. So, I guess that business is looking for more effective ways to advertise. Also, I think that gambling platforms have a bit deeper pockets and bigger budget for advertising than some no-KYC exchange. After all, gambling campaigns probably is just more effective - we have so many people here who actually gamble
Yeah, it's true social media like Facebook or youtube have strict policies against the gambling related promotions that could be one of the reason why we don't see them but I have seen stake advertised by many creators like shoutout for them for being the sponsor of their video so they exists in social media too but in different way.
No, it's not that strict. Everything depends on local laws. If in your country advertising of gambling isn't allowed, then you won't see it on Facebook or Youtube. In country where I live, these websites is full of gambling ads.