I am not surprised of the above mentioned countries. What I know that could thrive the extension rate of gambling in a region is either due to economy structural stability with the governments focused on the welfare of her citizens and residence.
So the above mentioned are all of global economy influential countries whose economy news could have effects on other countries in the globe.

Sometimes what strives the increase of gamblers in such states is too much comfortability where residence does not stress too much to earn money for living.

So they probably lack financial management which also prompt investors to invest more in expatiating the betting ecosystem and while they may tend to provide the masses the interesting services is the more it residence are gambling while the bet company owners are making more money in the sight of providing the players their exciting gaming services while they may play for fun and likely get carried away.