Men provide more with their skills and commitment, so they get promoted quicker and have a wage gap. Women prioritise their family and their children over their jobs, so they earn less.
Murdock:
women were located in the home because of their biological function of bearing children and because their physique meant that they were less able than men to perform strenuous tasks
Rastogi:
men and women serve different roles and functions in society and are rewarded in different ways. Men are work oriented and committed to their jobs whereas women choose to prioritise their roles as homemakers and caring for family over their careers.