Replace "gambling" with alcohol, drugs, and tobacco, and you get the picture! How do you stop addiction when some don't want to stop it themselves?
In most of the Western world, there are help lines, NGOs, associations, and every kind of help possible to cure addiction but most don't approach them they stop the counseling, they relapse in less than a week, and so on!
Well, you could stop addition, you can go fully North Korean style as there is no problem with drugs or gambling here but would you trade your freedom from something that most people can take care of themselves? I woundn't!
The most effective means to reduce gambling addictions by a government will be to create jobs that keep the majority of the youths in the country engage and busy, and also providing a good economic empowerment for their citizens, this way no one will have reason to gamble, because many of those that gamble in most part of the world does that for means of making money.
Gambling addiction is older than workers' migration, Great Britain banned gambling in 1541 because of addiction and people making debts:
https://en.wikipedia.org/wiki/Unlawful_Games_Act_1541Besides, people need money to gamble, if they have money then it means they work!