So my question is, is the percentage of the rich gambling lower than the middle and lower class?
People are really not content with what they have, even when there is enough money. Sometimes it's just not enough for us. There are people who are okay with what they have, but some people are not, no matter the amount that they have, so that your friend might be right when you look at it from some point, and he can also be wrong in other aspects.
I can be a very wealthy man today, and I can provide for everything that I need in this life, but since our wants keep on increasing every day by day, I will still have to try my luck sometimes in gambling games to see if I can win some money and add to the ones I have and maybe use them to quench my thirst for some wants.
On the other hand, there is also a possibility that I might not have money to foot my bills, and the little I have can't be enough. For me to solve those pressing issues, I will have to use that little that I have to gamble and see if my luck can let me win and I can use that money to solve my problem. There are people who are like that in this life, and that's their reason for gambling.