A considerable amount of people came into my mind after reading your question because I think the most vulnerable are the middle class and poor people, underage gambling as youth adults search for ways of earning money hence most of them rely on gambling to give them money but instead they lose to gambling. People aren't being sincere about how much they're losing because the figures has to be massive for casino to be running their business and opening different branches in different states. Teenager are vulnerable because they don't yet know how to avoid being influenced by gambling and they think everything will go according to their plans they make but get disappointed when they don't meet up the expectation they were setting. Teenagers that are well disciplined don't get addicted but those that aren't and only running after the money, end up worse.