I prefer strategic gambling with amount that I can afford to lose. No gmabler become suddently rich by gmabling, let alone being billionaire. But, by running a gambling site, you can definitely be a billionaire. 
You are right, gambling is not a place to become billionaire but it is a place for entertainment and members play there for getting fun, and they are provided by the owners as their business so only they have the right to earn money there. The rich people which you see in casinos are not rich because of playing these games but they are already rich with their businesses and they come there for fun only.