Same as any other casinos or business out there, they do advertising but they're all using different kinds of advertising as there are some that employ a conventional one like commercials and ad placements on TV shows and radio stations, some are even utilizing social media, some are even building a marketing team that will create the branding, the pamphlets and other marketing implements. There's also the Internet that hosts millions of advertisements from millions of companies all over the world and with almost everyone interconnected by the World Wide Web, this is probably the most efficient way to advertise your product, business or services. Signature campaign is a unique one though as it's not going outside the forum so it's limited in audience but it still somehow works.
Every advertisements out there is limited in audience bud, for example, TV ads are limited to those who watch tv, as not every one watches TV this days, radio ads are limited to those who listen to the radio.
And when it comes to the internet, ads on Facebook are limited to those who use or are on Facebook, Twitter ads are limited to those who use or are on Twitter, Instagram, TikTok and the rest of this social apps are all the same based on ads placed on them.
And this is also the same when it comes to ads on sites like coinmarketcap, coingecko, etherscan, bscscan, dextools, poocoin and so all, all the ads are limited to users of this sites respectively.
And this is also same for bitcointalk and every other forum, ads here apply same rule as it is on other platforms, that is, limitation to users and visitors of this forum alone.
There is no platform out there where ads on it are shared or transferred across every other platform that exist, as an advertiser, if you want your ads placed or shown on multiple places, or platform, you will have to pay for it respectively.