I know of a very big betting house around my area. The employer only employs girls to work for him. He has close to about 10 girls as staff working for him and he made a young guy as the manager to be covering and run around for the affairs of the betting, to keep it going.
I think this might be one of the reasons for his taking such a decision of employing only girls cos he knows the dangers he might face in employing guys at times runs in the betting house
Most establishment hire girls especially teens that have a good figure to attract customers. It is part of the marketing strategy of the owner. I do not think that the reason why the girls are only hire is because of your stated reason. Admit it or not, in an establishment dominated by guy clients, the best thing to attract them and return is to have something that interest them. And this time the best lure is hiring girls to serve in the establishment.
I think it's important because this can cause job-related conflict in the future especially if an employee is really addicted to gambling. That doesn't mean that his not fit and needs to seek professional help first. If the interviewer would get to ask any gambling related questions, he should not ask them directly because it might offend the applicant. He should ask it in a good manner.
The reason for an interview is to get a bit of information from the personal background of the person. So questions like addictions and stuff can be asked directly to the applicant, of course it can be asked in a rude manner or in a nice way. This depends on the interviewer besides it is the applicant that needed the job while the employer have way more option to fill the job.