Everyone has a different personality, some are open with the gambling they do and some are closed and no one knows about their gambling activities. This will return to each of us. However, in my opinion it is more dangerous when someone is closed, because when they experience problems with addiction, they will feel it themselves and no one can give them advice. The role of other people is also important in my opinion, because when someone gambles excessively, there will be a kind of brake from other people who warn them. Yes, even though it will return to each of them, at least they can realize it faster because they get advice from other people.
There's a reason for someone to stay private, it's because social expectancy.
You know, many companies not want to recruit gambler, parents not want their kids to be a gambler, not to mention friends and partner don't like gambler. That's why they need to hide it in order not to be ostracized.
But, they should able to seek a professional if they feel not alright.