Answer

Truthfully, the prohibition here is not clear. On the face of it, the Talmud seems to indicate that this branches off from the prohibition of theft (because a conditional commitment does not effect acquisition, although in Sanhedrin the Talmud implies that, in practice, the halakhic ruling is that one who plays dice is not considered a thief, but the halakhic decisors disagreed about this).
\This is an excellent example of first-order and second-order halakhic ruling. People quote the author of the Shulchan Arukh and the Rema, who disagreed about this, as if there were a halakhic dispute here that pertains to Ashkenazim and Sephardim. That’s nonsense. In order to discuss whether there is a prohibition in such games today, one has to examine whether in practice people really do not have full resolve of mind. It has nothing to do with the author of the Shulchan Arukh and the Rema and other precedents, since every place has its own circumstances and issues. I think that nowadays people usually do have full resolve of mind, and therefore there is no prohibition here according to all opinions.
However, dice players are also considered people who neglect the world”s productive activity (they occupy themselves with nonsense and empty matters), which is not really a prohibition but rather a disqualification from testimony. But here too, in a case where this is organized entertainment done systematically and bringing in money, and not just addiction to idleness and nonsense, there is room for it.