There are many platforms that mixers can use to conduct promotional campaigns for their services, so I tried to find an explanation as to why they prefer the forums and insist on them, even though most if not all of them cannot be compared to the BitcoinTalk forum, and it can be said that they fail due to the lack of traffic on them.
The only logical explanation that I found is that all the rest of the sites refuse to place advertising banners for Mixers, knowing that as far as I know, there are no laws or legal conditions that prevent them from doing so (at least until now).
Because the community or forum is dynamic, people will stay on to read all the discussions compared to an advertising platform which will only show the platform site or banners, mixers will always have markets, and their clients will follow them on whatever platform they choose just to see if their service is still up to date the proof that they have a huge market is the amount of money they pour just to advertise their service if they can allocate huge funding then there's a big probability that they have existing and loyal clients.
The mixer's ability to spend on relatively expensive advertising campaigns does not necessarily mean the success of those campaigns, because it is very important to choose the promotion platform. Users will follow the official channels of the Mixers to stay updated, but this does not mean at all that they will remain on a forum that does not have content that attracts their attention, because they will not spend their time just seeing signatures bearing the names and links of the Mixers without having another clear goal.
The idea came to my mind of launching a site like Bestchange, where mixers pay the site for listings, and the site works to promote the listing services without referring directly to the mixers. The idea can be easily implemented technically, but there are certainly other obstacles that are absent from our awareness.