I'm not sure you have really checked different bet sites and casinos to really know if they put up ads about the dangers of gambling. It's always written boldly when you log into legit bet sites and casinos to gamble responsibly. A lot of casinos are willing to curb gambling addiction by blocking the account of gamblers when it's getting out of control but of course you must reach out to them first for them to know
Yes. They won't do it if you don't tell them anything. That's how gambling businesses work. But if you do tell them about your gambling problem, then perhaps they will block everything, including promotional emails.
It's different when it comes to drinking. It's obvious when a person is an alcoholic, and it smells. A person who is an alcoholic doesn't even need to tell anyone that he is one. It can be seen physically, although it's still up to that person if they will seek help. No one can force him unless he did something wrong to other people or he ain't good for society anymore.