Or have you played in this kind of underground gambling den before?
People are allowed to have a gambling business in my country and citizens are allowed to play so far the person is already 18 years of age or more. Underground gambling are illegal gambling but if gambling is legalized in a country, people will prefer to get registered instead and make their gambling sites legal. This is better than trying not to pay tax but in a way the gambling site can be known and shut down by the government.
I have many gambling platforms that I can use legally, then why underground gambling? As for the online illegal gambling sites, they are not located in my country and I avoid them because I do not trust them. I play on foreign sites like Stake, but that is because they are not illegal but legal and have a license.
You are actually right about this because in my environment the only hideout gambling which of course can as well be referred to underground gambling are that of the illegal gambling activities which are more of face to face gambling, people tend to hide and have this gambling done in other not to attract unnecessary attention from the public and government authorities because they are illegal and have no license to operate and in most instance guys indulging in this kind of gambling are usually in to some hard drugs and they are always on the run from government agencies.