The closest people will know that you gamble no matter how it will be hidden they must know it, now imagine gambling is almost everyone knows even though they never play for example.
There will be more people covering up their shame than saying that they are addicted, which is clear that they know how to do it, they just don't explain that they also have the same problem.
Whatever habits we do, of course the people closest to us will know about it and we can't hide it from them, yes of course everyone knows about gambling even if they don't play it and we won't be able to hide it and it would be better for us to gamble by limiting it. the bets we play so as not to have a bad impact on the people closest to us, of course each person will not reveal themselves to be addicted to gambling and they will continue to hide this habit so as not to disturb the people closest to them.
I don't think it will always be known especially if the gambler really keeps his gambling activities secret especially from the closest people such as family members especially if their environment strictly prohibits gambling activities, but it is a fact that over time they will eventually be found out by their families about their gambling activities, that's because over time the finances of a gambler will usually be disrupted especially if they are one of the irresponsible gamblers in the sense of always chasing victory or treating gambling in an excessive way.
True, gambling by applying limits along with applying management to budget allocations is a recommended approach and indeed this method is one way that we can slightly avoid bad possibilities which of course will not only harm ourselves but as you say that can also have a negative impact on the people around us, as much as possible we should be able to maintain and manage it properly.