Because I've had to try and explain it to you and you don't understand.
http://www.dailymail.co.uk/femail/a...en-state-start-working-free-compared-men.html
In fact, the pay gap persists across nearly all occupations: female CEOs earn 28 per cent less than male CEOs, female lawyers earn 23 per cent less than male lawyers, and female computer and information systems managers earn 18 per cent less than their male counterparts.
I assume they "chose" to earn less, yes?
Bare in mind that comes from your spiritual lords at the Daily Mail.