In the past a woman's life was all about raising her children.
As she was nursing, and her child still depended completely on her body for it's nourishment, her own body got a chance to recuperate and rejuvenate itself from the toll of childbearing.
Since her children were her only goal, she didn't require any "me" time. She wouldn't understand the purpose of "taking a break".
Things are different today with women working and centering their lives on things other than childrearing.