Why does it seem that many women cut their hair short after their first child?

I realize that I am generalizing here and apologize ahead of time but, to a great extent, it seems that if they are going to cut it, that within two years of childbirth is when it happens.

Does it have to do with having a child pulling on it gets tiresome or painful? Is it that the shorter hair is easier, quicker and less trouble to take care of when you have just added a great load of responsibility to your lifestyle? Is it that shorter hair is perceived as more mature in nature?

What is the driving force leading to a shorter hair style?