Some people that are addicted hide their gambling activities because they believe if people notice the amount they spend on gambling, then they will be blamed. Some people might end up spending money that is supposed to be spent on their family members on gambling, which is wrong, so they won’t want their family members to know they are spending that amount of money on gambling.
Also, for some people, gambling is illegal in their religion, and most of them want to gamble, so they will rather gamble and keep it secret so that people won’t see them as bad people, so they decide to keep it a secret.
Anyone being responsible whenever gambling shouldn’t have to hide that they play sometimes.
A man who gamble irresponsibly may simply want to hide the fact that he’s gambling irresponsibly. And when it’s hidden from friends and family that could talk some sense into him, it would gradually turn into an addiction and when it gets to that point, it then becomes not so easy to hide anymore.
Asides from being an irresponsible person who could spend money budgeted for something really important and after losing out, would in shame, try to hide what actually happened to the money and perhaps also for religious purposes, I see no reason on why someone, despite being responsible enough when gambling would want to hide the fact from anyone.
It’s one thing to live a private life and it’s another to actively go the extra mile to hide the fact that you gamble sometimes for fear of what people might say.