Let's assume that a country has a better economy but its people can not realize the effects of gambling, they will still gamble and maybe many people will become addicted. They will deeper into gambling and face the gambling addiction problem.
monaco not allowing their citizens to gamble despite most of their citizens being millionaires at least may be an example of this
they will not appear in any data because their people do not gamble in their country and would have to go to another country just to gamble so addiction may be easily prevented