Why less women choose IT as career

Being a computer engineering student, when I loook around myself in the lecture theatre, I find a large number guys with a handful of girls. And its true, my university has only 20% girls in computer engineering course, that means for 4 guys, there is only one girl!! Check out Opening doors for women in computing at news.com. They have also pointed out that there are fewer women than men in IT industry.
Why is that so? I refuse to buy the argument that men are better than women at logical thinking. I think that it is the way women have been brought up. It is the so-called traditional role of the women to take care of family and kids. We tend to discount how hard women work for their families unless it is some high-paying exotic job. So there!