Gambling will become illegal if they don't have permit or the gambling games that they play is not authorized by the government.
In my country many people are gambling illegally but sad to say some of them are only caught but maybe that is their only ways to earn money like weteng who is very illegal to my country. But in my country gambling is not commiting like crimes and I do not why Bangladesh are treating it like a crimes.
Maybe the government thinks that gambling treats as a crime because that can trigger people to commit crimes such as robbery, stolen other people's money or else. So they regulate gambling as an illegal way to make money. But still, people will search for illegal gambling as in that place, people can try to play the gambling games, and sometimes they can play traditional gambling games which they already know before.