I will like people to learn from this because many people gamble in secret for what ever reason and the have companions who knows nothing about this and when exposed can cause the relationship to split or have cracks.
If you gamble it is of your interest and that of your spouse, you both need to share same orientation about gambling or given a chance to understand and respect the other person gambling choice and if they won’t then either they go or you reconsider your choice. Why should an adult keep their gambling choice away from their lover that’s deceit to me. Gambling is not a dirty secret.
Others who keep it a secret know that they're not going to be trusted by their partners. And so, instead of telling it to have a common interest in their relationship, they won't tell it because they will be stopped and misunderstood, misjudged.
I agree to you that it should also be informed to the spouse but, it's understandable why many keeps it that way.
They don't want trouble, and they want to gamble peacefully without anyone trying to stop them and telling them that they should do other things than spending their money in gambling.