Talking about professional gamblers. It is already a person who knows their responsibility and risk. They become professionals because they can handle themselves more than others. So I would say there is no issue with them and nothing to worry about with these people because they know what the right thing to do is. We just assume the wrong thing.
At first they may not be any issue but remember professional gamblers are still human, they have feeling, emotion, greed, carelessness etc... Everytime they engage themselves in gambling, they are always expose to gambling addiction. In fact, here is
one of the videos about professional gambler turned into a gambling addict.
That is why I have big respect for these so-called professional gamblers. There are few because only a few gamblers do right. Of course, they are rich gamblers who are not afraid to lose money.
Professional gamblers, albeit practicing self-control they are also prone to temptations, irrational decisions, and getting hooked and of course addiction.