It is cowardice to hide your gambling habit from your spouse, you can decide not to tell another person but your spouse is your companion till death or divorce. People should be open about their likes and dislikes before marriage, it is good to discuss everything so that nothing will come as a surprise to their partner. It'll be deceitful to learn that your husband or wife has always been a gambler if they told you otherwise before marriage. The spouse at the receiving end will find it hard to believe anything said by the lying partner afterwards. Better to let everything out before joining in marriage so your partner can accept you for who you are or move on.
Mate you are right, I think as married couples there shouldnt be any kind of hidden stuff that exist among you two right from the beginning even before marriage just as you've noted down here especially when it comes to things like gambling, people feel that they can just out smart themselves forgetting that no matter how they try to hide some stuff, a day will come when such will eventually be made open or noticed, your partner should know if you're a gambler to know if he or she can adopt to such, infact apart from gambling I think your partner should know you intimately to avoid some issues as time goes by, these are even things both partners are suppose to know during the dating stage so that there wont be any form of unexpected surprises that may lead to doom, you know what I mean, your comment is on point.