One billion Chinese, just think if 5% from them are gamblers. And from them 20% win - it is 1 000 000 
Think of the profits the other 80% are making to the casinos. 
One of the best investments is being part of the House in a casino
Always make profits in the end.
As for why Chinese tend to take risks its because they want to be rich quickly and not live as modestly, that and they have a lot of gambling games hard to stop once you start.