Money runs gambling. It gets transferred from a point to another. From the poor to the wealthy, from the wealthy to the poor.
Let's first talk about how the poor gives the money to the wealthy.... They allocate a huge part of their money (which isn't a lot in the first place) to gambling thinking that this would be the quick fix to their problems. This is how they give the money to the wealthy in this case the casino owners.
But the money can also go from the wealthy to the poor. If the tax from casinos gets collected by the government and is used effectively, it can help a lot of those in need. The money can be used to improve infrastructure, education, healthcare and etc.
But the tax is not used effectively in 98% of the countries. Mostly in the African Nations, taxes are not even used but to enrich themselves. So I don't see any good distribution of money in the gambling sector. And any country that allows an individual to operate their own large business is not good in equal distribution of wealth. But it is when the government control a Large number of business then the circulation of wealth can go to the vulnerable.
We have seen this in our neighborhood countries. The rich people gamble and the money return back to them and the poor loss it all.