One person in the couple handling the finances often leads to major problems, either through divorce or death, according to Bloomberg in "Rise of 'Gray Divorce' Forces Financial Reckoning After 50."
Most married women will outlive their spouses. They might not even have a spouse to outlive, because divorces for people over 50 are becoming increasingly common. The result? An elderly woman who relied on her husband to handle their financial decisions, may suddenly be forced to do so for herself. They often make expensive mistakes in the process.
The best thing for everyone would be for married couples to make important financial decisions together. That way neither of them will need to learn how to handle finances in their elder years.
Reference: Bloomberg (April 13, 2018) "Rise of 'Gray Divorce' Forces Financial Reckoning After 50."