Do they? I've seen women take 6 months or even 3 months maternity leave, with their partner stepping in to support.
For what purpose are we saying such crazy things? Why is it so important to place all members of the human species on the same rack, stretch them to the same length, and maim them till they fit?
How have we, as a civilisation, become so terrified of difference?
Also, 1.5 months off prior to the due date is more than normal. Most women work until 2-4 weeks before.