This is more than wrong because minors should not be involved in gambling, moreover it is an offline casino. And if the casino does not immediately implement strict rules that prohibit minors, it will be fatal because more and more minors will follow them. And if not immediately, I'm sure people around or people who don't like it will hold demonstrations as a deterrent effect.
In the country where I live, minors are also not allowed into offline casinos to gamble or just watch.
Age restrictions must be specified in online and offline gambling regulations so that no one under 18+ is involved in gambling even if it's just watching. I have never seen children gambling at my location and they seem to have an understanding that adult socialization is inviolable and not followed by those under the age of 18+.
There are already age restrictions that have been set by these casinos however it is just not that implemented properly as guards don't really require gamblers and customers to show ID which is why there are some minors that are able to go inside and gamble especially those that can't be easily identified as a minor.
At most of the local casinos, I've visited I sometimes encounter young gamblers between the ages of 16-20 as you won't be able to identify their age until you ask them personally.