This happens because women are raised to be terrible negotiators. http://books.google.com/books?id=k6vd7PJUFmYC&printsec=f...

Its the way we (women) are brought up in the western world. Girls are pushed to be consensus driven from a young age; whereas, boys are encouraged to participate in conflicts. Its playing house vs. playing war analogy. This translates into women avoiding and being uncomfortable in conflict situations, even salary negotiations.

But it can be changed. Awareness amongst parents is the first thing. Growing up in India, my father told me I could achieve anything I wanted. My mother took me to markets to bargain at a young age. As a result, I am not afraid of conflicts. My mantra is: If you dont ask, you will never get it.