I believe the culture is the main factor why some countries have more gambler compared to others.
Like in my country, Gambling is very popular because old generation use this as leisure time that’s why new generation like it too since we knew that old generation enjoy playing this.
We are not rich country but we are hardworking which is the reason we get fund for our gambling habbit.
Yes, I think you're spot on. It really depends on the country.
That's pretty much the whole thing, it's part of the culture. That's what makes the ads actually legal or not, really.
I think as you say, it is not dependent of the level of richness of a country.