It will depend on their target.
If the casino is an onlinegambling platform under cryptocurrency then this forum is a big factor as most or all crypto enthusiast are on this platform. This is a big deal of the mainstream media of crypto.
If the casino is on Fiat or on localbound of a country, Then advertising on TV, Radio and poster are enough, Streamers on social media is one of the best platform.
The casino full supported fiat actually focus advertising on Television, Social media platform such as Facebook, TikTok, Instagram but if casino gambling platform with cryptocurrency will use forum for advertising. Before advertising, the casino gambling has target about what the user will see their advertising and what kinds support of the casino gambling available deposit trough fiat, local bank or using e wallet.
Right now the gambling casino advertising at social media platform actually Facebook how many time seeing the fanspage link promote the casino website.