I don't think you should hide anything from your spouse, and that includes gambling too. Gambling addiction is bad on its own, then hiding it from your partner is a betrayal. Gambling has to do with your finance, so it's very important you share it with your partner, so you both can even make a budget for it, so it does not affect your finances.
Hiding your gambling habit from your partner could lead to divorce, when they find out that you have been hiding it from them. They will definitely feel betrayed and it's really going to affect their trust for you, and when trust is broken in a relationship, it's might lead to a divorce.
I have to be agreed with you about this but still its matter of regional as well because still in few countries specially in subcontinent this is not problem even here gambling strictly prohibited but too many involved and having this as addiction.
Joint family system and arrange marriages always encourage things like these because both never talk about this and after marriage mostly never want to live divorced life which encourage things like these few families which understand consequences always done strong decisions and fixed this.
Its matter of education and allowing women to have some skills which always give them confidence and courage for taking strong decisions can make things better.