I can't understand why anyone would need to tell anyone about your gambling, much less your wins and losses. Although most likely the only thing you will have to tell is about your big losses. If you get into debt and it affects your family, then talking and information about your losses is inevitable. As for winnings, the situation is different. Firstly, it is a very pleasant thing. Everyone likes to win, especially if the win is natural. And in most cases, you are not obliged to tell anyone anything. And unless you have won a large jackpot (and this is an extremely rare event), then most likely it will be easy for you to hide information about your winnings.
It is about either venting ones grief or flexing ones winning to other to feel better about oneself, in my opinion. It is a very common thing to see in this modern society around us which encourage people to "be a winner".
For example, when you log on social media (specially Instagram) you will always encounter people having long trips, having luxurious dinners in high end restaurants, driving expensive cars and stuff like that, so collectively we are getting trained to grab about things we have (and even lie about what we have) in order for us to feel better than others and as a coping mechanism.
That translates to gambling, when people lose money, they do not jump onto social media and immediately let know everyone they have lost money to a casino, they stay silent and bite a bullet. On the other hand, when someone gets rich out of their own luck, they start to talk about it to their family members, to their friends and acquaintances, that is how society is training us.
Because,m in the end we do not fully know those people around us, some of them could develop jealousy against us, there is where most of the problems originate from.
there is a good reason some people believe money is that root of evil.
Aristotle, 2500 years ago, in his
Nicomachean Ethics, spoked already of what you describe here.
For him, virtue is in balance, and in II, 7 there is a list of virtues, including TRUTH:
With regard to truth, then, the intermediate is a truthful sort of person and the mean may be called truthfulness, while the pretence which exaggerates is boastfulness and the person characterized by it a boaster, and that which understates is mock modesty and the person characterized by it mock-modest.
We usually talk about what we most often see, or what is more salient to us: the boasters. But I think that most of us don't brag about our winnings, either out of modesty or out of fear or security. The same happens with our Bitcoin hodlings: the general advice is not bragging about our savings, but we all know famous exceptions.
The case of the people who go so far as to invent their success, unless they make a profit from it (and even if they do it), I think it's pathological.