I'm sure those elderly ones won't like to be there missed up with young ones who can even resort to abusing and insulting them at any slight provocation of stepping on them. A young person who loses his bet could be angered and could get on the nelves of the elderly which could result in a fight.
On the contrary, old people admire the boisterous nature of youthfulness. It reminds them of that stage they once were in. Except young people are way out of line, elderly people like the company of youths; especially youths who share the same vices or pastime with them. It gives them that validation of youthfulness which, anyway, is a sham. This search for inclusion is more predominant among elderly people who've lost friends and families to death. Look around your locality, you will discover this truth. So, I don't think elderly ones will have issue with youths when mixed with them at casinos or betting shops.
As long as everyone is happy with what they are doing, they can always pursue what they want to entertain themselves. People meet a lot of strangers everyday, so it is up to them how they will interact with people without causing any trouble.
So if they are gambling to have some sort of collaboration with other people, why not? People need companionship to stay relevant so to speak. They need to have human relationship in order to stay alive. If not, what's the reason of living each day of your life? Unless, you can live alone and have fun at the same time.