As for how it is in my country, well, the elderly people are not gambling as such, there is no way they will be gambling so much that I will not know about it as I move around more often. It is the middle-aged people who mostly gamble in my opinion, and if the elderly ones are gambling indeed, then the population will be lower than 0.05% here.
A younger age is added to the average age of gamblers (in my country). Even more so, underage young people. I have personally seen people who bet on gambling on a regular basis. This is facilitated by the easy availability of mobile (gambling) apps, smartphones and the internet. Almost from childhood, people already have access to all this, which allows them to make a very early start in gambling.
I don’t have detailed statistics, but in my region the number of active gamblers is more skewed towards younger people than older ones. Of course, old people also play, but in incomparably different proportions from young people.
To be fair we are talking about different styles and that seems like the case. Elder people do get together a lot more outside, it could be some cafe that is designed for this, or it could be some special place, it doesn't really matter. We see a lot of elder people get together and play backgammon or chess too, it's just a way for them to keep contact with life, normally they are retired so they do not go to work, what is the alternative? Stay at home all day? Of course not, they go outside and meet with people, make friends, and play.
I think you are getting this all wrong, and this is simply because you've not followed up with the communication from where it started so it's obvious you did not get the gist. First, it is not about retiring and becomes idle, there are other engagements that could be religious, humanitarian, social welfare and productive personal engagements. Are these not time occupying enough? This is a set goal which is personal, so anyone may have their own plans for their lives which I wouldn't want to poke my nose onto, not to mention questioning it.
Secondly, your point about seeing the elderly ones everywhere playing games is just baseless to me because no one says he can't play games and have fun at an old age but saying Gambing will be avoided at that age, which is personal. Or are the elderly people you saw told you they gamble all the time they play the games?