Clandestine gambling shouldn't exist, but it does thanks to the poor management of the governments of some countries who think they control everything Clandestine games, when they are "normal" games, seem fine to me, because each of us has the right to decide how to have fun. But when things are done that go against human or animal rights, that's wrong in my opinion.
To the country where gambling is banned: their government uses excuses like gambling promoting crime and overspending by their citizens or because it's against their majority religion beliefs, which shouldn't be so.
Everyone is supposed to be given free will to decide how they want to use their money, and if possible, an agency should be set up to monitor citizens' gambling habits. Rather than banning it, they don't know that the more you try to obstruct things, that's how the citizens will look for possible ways to satisfy themselves.
The fact that there's huge amount of money in terms of facilatating underground gambling, that's where those corrupt officials/politicians are involve, if not all are being own by those personalities most of them are protectors that's why this kind of illegal business do exist, like what you have said, free will that should be provided and allow people to choose if how they wanted to be entertained, though they just need to monitor and put rules to prevent heavy addictions resulting to some crimes that might be cause of gambling participation.