The government can ban gambling but it doesn't mean they can ban people from accessing illegal gambling. Banning gambling will give more negative result than regulating it. If a government banne gambling the citizen who are engaging in gambling activity are now breaking the law, they might get imprisoned or put to jail where the government shoulder all the expenses of the prisoner. The banning of gambling activities doesn't prevent people from gambling and becoming gambling addicts.
So banning gambling is a loss, but regulating is I think a win-win scenario.
Indeed, citizens who are convicted of gambling activities will be just another burden to the government whom they will be forced to get the citizen food and shelter while in prison and that means exhausting funds that could be used in another way that is more useful. Banning gambling won't be useful and won't get the citizens out of the activities nor get rid of their addiction.