Why are expectations for men different than expectations for women?

When a man does something, he needs praise but that same thing is done by a woman every day without thanks. Why in the history of the human race are women always expected to handle more? How do we change our way of thinking? Yes, in the past men worked (hunters-gatherers), so women were the home-makers...but today is a different time. General discussion becaues I'm curious on peoples' opinions.