Very few Asian countries are available in the list. As per the data, western nations have good number of gamblers. The amount being spend on gambling by an average person from the top countries is really big when calculated against the fiat currency value of third world countries. For some people it is one year's earning through their daily job for the living.
seeing from the data above, my country is not on the list, which means there are still very few gamblers in my country...
It is true that Asian countries have few gamblers but not a few players from Asia who play in western countries or the US. if we look at 'spent on gambling/year', the countries from Asia are in the lead.
We know that Asian countries have traditional gambling games, so I think that does not count as gambling on that list. If they count the traditional gambling games, I think the Asian countries will get on the list. We do not know what their indicator to list the countries that playing gambling, so we can just accept the list. If we want, we can search for the other sources to see the other countries that gamble the most.