You have said truth yourself, the better economy has country, the more «free to use» money their citizens have. From the article and picture in it, we should cross out USA and Macau, because of Las Vegas and licenses, these countries will always be in top among gambling. Rest countries that are on the picture are counties with most powerful economy. I know that for UK is already part of a culture to place a bet on football, sports betting is so developed there, that they have places to place a bet almost on every street. Also we can go to a religion. It matters a lot. Not a single country with Islam religion mentioned in that article.