I am very surprised that Japan is in third place on this list. The thing is that it is a rather pragmatic country. Yes, they believe in their religion and spirits, but are they as superstitious and gambling as the Chinese? Statistics say that they are. Apparently, Asian nations love colorful casino interfaces, and similar to their love for computer games and entertainment such as rooms with different slot machines, Japan guys like the atmosphere of gambling.
I guess that could have something to do with their karma-based religions. People feel that they could be luckier if they are entitled for good karma etc...
Also to my knowledge there are some numerical superstitions that could play a role in gambling, even though China probably outranks them of that.
If you combine combine numerical superstition with idea of karma, then everything else seems like overthinking because gambling seems like obvious result for it.