The thing is that porn sites and casinos, as well as bookmakers, often have the same audience. This explains the phenomenon that casinos and bookmakers often advertise on porn sites. Porn site visitors are more often men. I don’t know how often women watch porn. I suspect that very little or they hide it very carefully. In principle, I know that even within porn there are differences. I read an interview with a porn star, she talked about female and male porn. But in general, male porn predominates and casinos and bookmakers advertise precisely before these porn videos. Is this unlikely to damage the reputation of gambling sites? Personally, I doubt it.
Girls also watch porn videos, but they are usually excited not by video films, but by 3D animation. There are also special erotic video films intended specifically for women.
In general, erotic films are a huge money market. I even read an opinion that we owe such a rapid development of image transmission technologies to erotica. No one would make such perfect monitors and computers if it were not for the erotic film industry. Any technology needs a simple and fast monetization system...
At the same time, the erotic film industry, as well as the gambling industry in many countries are in the "gray" zone - that is, they are not prohibited, but also not officially recognized.
In this regard, both of these industries experience certain difficulties with advertising promotion.