Everyone has their own thoughts and decisions about what their partner can and cannot know, so I personally can't say "I agree/disagree" or "you're right/wrong."
If I personally, when I decided to get married, we both agreed to be open with each other, to make decisions involving both parties, and to have no privacy because it's all for our own good.
Especially regarding gambling, which could one day affect my mood, finances, and financial management, I have to tell my wife so she understands and can monitor me to prevent stress or addiction.
You are correct that everyone has privacy and everyone has his/her own opinion but it is open discussion forum and evryone here posting based on his/her life not based on others. But for me and my friends whom I know best way is not to share with our partner as it may happen something oppose at the bad timing.