Not everyone who is well-dressed is mentally stable. Some addicts are mentally unstable, without noticing it, despite being well-kept and feeling in control of their actions. The man in your story is not causing any trouble to anybody in the gambling house, he is only not well dressed. Which is not anybody's business, provided that the gambling attendant is comfortable with him, no problem.
It is not only about the gambling agent but also about the other people that are gambling there. There is no problem if other people are not complaining about him. Not to be well dressed in public can make some people to know that he is mentally unstable and not like to go to the gambling place because of that but they will complain before not going. I think it is a betting agent place and it will not take more than 2 minutes that the mentally unstable person will spend to place bets and that gives him advantage.
Secondly, he's not begging for money or aggressively disturbing his parents for gambling funds, like many other gambling addicts who suffer mental disorders do to their loved ones. He's doing his job and maybe may have been conditioned the way he looks due to the kind of work he does.
He has no job. People are using his condition to give him money.
I don't know if you're aware of the person Op is describing in his thread, but from what I read which led to my response, Op said he does a manual job. I'm not in Op's location nor do I know the man, so not in the right place to push further with your response, which says he has no job. However, he doesn't have a job, I mean continuing from your response, I have things to add. A beggar that uses his money to gamble, I think is deceiving the society or not in deep need to be a beggar. For a person to beg, he has nothing, no food, no family to provide for him, etc. It's not common to find a beggar who uses charity from others to gamble, maybe he's not comfortable with what the people are giving him or is turning begging into a full-time job. People who are worried about the dressing of another person in a specific environment don't understand the differences in people.
Personally, looks and dress shouldn't bother people. Their business there is to book games and go, and if they're not comfortable with the type of people visiting the gaming house they can stop going as you said. Which shouldn't be a problem for the agent. The customers there must find a fault, regardless. Finding a fault from another customer as a reason to stop patronizing the agent should also be tagged a personal problem or lack of emotional intelligence provided the customer isn't aggressive, fighting, or destroying their property. What matters is the serenity of the environment. How would you feel if in a barber shop, you walked in and found the same man being barbed in the same seat you'd sit next to Barb, would you leave the environment or not? I'm asking this to be able to understand your behavior toward such people, not just about what other people would do or say. I'm not sure if you are close to Op or have seen the man in his story.