I think keeping your activities as a gambler a secret is also a positive thing when you try to keep it a secret because in this case the treatment or view of each person to gamblers is a little different. I don't know about other countries but in the country I live in, especially in the area I live in, the stigma of "gambler" is seen as someone who has a bad habit and is viewed differently.
Even though there is no prohibition for us to gamble because it is the right of each person but still the view will be bad so that when we say clearly that we are a gambler then surely we will be labelled as a bad person.
For some people it may not be a problem and tend to ignore people's judgement but for others of course it is very disturbing so it is better to keep it secret than we end up being seen differently.
Keeping your gambling habit a secret is at some point important and necessary because some persons can real become dramatic and discriminate you when the get to know you gamble but then it's really funny how they would love to benefit from the proceeds you make from gambling with you, nevertheless don't make it know to such person if you have them around.
In oder to avoid that stereotypes and been seen in a perspective you wouldn't find comfortable and ideal it's advised you keep your gambling habit a secret when necessary but amongst your fellow gambler where you are sure of not been judged you can speak up as you can as well share ideas which can be of great help in the way you approach gambling.
It's sad that most persons have a stereotype for gamblers due to what have been seen of some gamblers out there who probably got addicted and became a menace to the society or probably resulted in unhealthy practice, this has made people find it difficult to believe that there are people who healthy engage in gambling and still have themselves under control.