Or have you played in this kind of underground gambling den before?
I heard that in the country where I live now there are a lot of underground casinos. This is due to the fact that the casino pays huge amounts of money to the state for excess profits, and any casino would like to avoid these taxes. Many gamblers easily find these casinos through telegram groups, and that is why there are visitors there.
I myself know about these hidden casinos from the news, sometimes on TV and on the Internet they say that another casino was found, and it was hiding under the guise of a bar.
There is no way such operation will last, the type of crime operations that last long are those that can be done by one person, secrets can be avoided compare to some hidden places where many people visits, even the visitors can be one of the betrayal to lead the law enforcement agents back to the location for few amount of money.
I don't know why people still visits such casinos this days when they can just do this online using regulated gambling platforms with no problem.
If you are in a country where the law doesn't permit for gambling I recommend you avoid gambling, if you get arrested in the process you already know what's coming next, avoid becoming a scape goat.