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.
Your points are valid, yet the funds cycle can only be efficient in a working government. If the government attend to it's responsibilities to the masses, then I can agree with you that it's a fair cycle because the funds from taxes are used for what it's intended.
In a failed government, I regret the distribution is one sided and the poor only gives to the rich and never vice versa.