Maybe that may happen to casino that lets minors playing gambling. But we know that the casino can do that easily and allow minors to comes to their place secretly. Not many teenagers have a good self control to protect them from the big risks of playing gambling. Teenage exposure to gambling can easily happen especially when they don't talking to adult people about what is the risk and the effect of playing gambling. But that is not a casino wrong because playing gambling or not is a choice for all people so they need to determine by themselves. If they think playing gambling can makes them lose too much money, they don't have to playing gambling instead doing other things.
Gambling is prohibited by law, as is selling alcohol to teenagers, but this does not mean that teenagers do not drink alcohol. The same applies to casinos, not all casinos require verification, but a teenager needs to think about where to get money, and how to send it to the casino to start gambling. If the casino allows a teenager to play, they will also be responsible for this, so this is not only a problem for parents who have not explained to their children all the responsibility for this.