In the UK male plus joint is roughly the same as female.
You also need to take the reasons into account as well as why. There are multiple reasons for this. The better off partner has more to lose from divorce, women tend to get custody of children, they might have different feelings of obligation to keep a marriage going (I cannot extrapolate this to other men, but I felt an obligation not to file for divorce until I had exhausted all other possibilities), social pressures and responses are different, etc.