1. Support from the government.
Countries who gamble a lot has solid laws protecting their players so gamblers in those countries can just freely gamble as much as they want without having to worry about their rights. This doesn't mean that the countries have very free and loose rules but it just means that they have clear frameworks. Some other countries have some limitations but since their rules are clear, many still gamble.
Most of the countries take the gambling ad their way permanently sources of income and that’s why we can see in some countries their gamble more than others as some countries just do it just for a fun, but apart from the others due they’ve have freely they can what ever they like about the gambling and the game they bet will still enter. I can say that is only few countries that have limitations to their gambling, is just that those are into it will be having control over their own finances.
I don't know that it is only gambling ads that make people gamble the most, there could be other things that motivates people to gambling more than anything. What I think allow people to gamble more is the law of the
country. If the government makes law that allow people to gamble freely like it is in my country, more people will gamble. Ours is even better because there are not taxes on gambling and people are allowed to gamble as much as they want, that is why the gambling industry is booming seriously in my country.