Maybe we have different views on gambling. But it seems to me that for society it doesn't matter if you are a good gambler or if you have an addiction and lose all the time, you will still cause bad emotions because of gambling. Society condemns such activities, so it is best not to tell anyone about it.
The OP stated things like belief and other societal factors that could result to such discrimination. It doesn't matter if the player is good or not, once everyone or family members discovers s/he engage in gambling activities they'll be seen as a irresponsible people. I've experience where gamblers are condemned to an extent that when they go broke people around them refer it to gamble as the primary cause of it. These societal attitudes are enough to make a gambler hide their gambling behavior. Definitely, a lot of people will celebrate when the player wins big, it's normal whenever we win people celebrates. Yet it doesn't remove the doubt that a gambler is wasting their money, especially when judged from the perspective of non gamblers. However, in those days before the institution of online gambling it was difficult to keep this a secret. Unlike today, players can carryout bets and nobody around them will know unless they open up to them; family and friends. We are advised to play responsibly and also take care of our other daily activities, even if we gamble, it shouldn't affect the next person who depends on the money for other things. For instance, gambling with family money or money meant for business.