Gambling companies have a responsibility to protect children and gambling addicts. They should not advertise on posters in poor towns and villages because people there have money problems. If they advertise in rich cities they should avoid schools and youth clubs. Gambling ads are a part of daily life for people who do not want to gamble.
Right, gambling companies are supposed to guarantee they have not targeting children and teen, that is relatively easy as there are spaces where children and teens are predominant. However, I am not sure what casinos are supposed to do when comes to gambling addicts.
Those gambling companies do not have reliable ways to know who is addicted to gambling and who is not. If someone gambles much on their casinos it could be just someone who is rich, not addicted to gambling. That is why self-exclusion exists and also declaration/proof of income; it is always necessary for the casino to have feedback from addicted gamblers, otherwise it is pretty difficult for the company.