Programming used to be a field with significant numbers of women, including true pioneers like Grace Hopper. IIRC, female computer science majors peaked in the 80s, and have been declining since.
Even with those low numbers these days, a lot of women who are interested in programming and computer science are chased away early on, or they quickly move into more welcoming fields. So it's true that among senior staff, women are even less well represented.
This isn't just a bad thing for the women who are harassed, mistreated, or just made to feel unwelcome. It's a bad thing for the industry. If women are unwelcome, we're throwing away half of the talented engineers before they even get started.
For all those reasons, Rob is right that role models are important. But even more important: we need to stop chasing women from the field. You have to stop the bleeding before you can start improving. The recent stories out of Uber make it clear that the technology industry is at risk of moving backwards if we aren't already.