I know of couples who don't know about each other's bank account. Basically total darkness. They don't know how much each other earns, how much they have saved, how much is insured, they don't know anything. Maybe they just contribute a fixed amount to a joint account every month for household expenses. Or they may split the bill very cleanly and everything is tracked very stringently.

Then there are also couples who share everything. They put all the money in the joint account regardless of who earns more. They go into their relationship wholeheartedly and believe that they will be together forever. The idea which was conferred to me is that if you keep things separate then there is an idea or fear that someday you will separate which is why you keep things apart so that it is easier to unwind.