Because they're nerds?
[...]money, success, and influence.
Oh. Well, I'm sure they'll stay in the field when the find themselves crammed into an open office, working on yet another webapp, with little to no control over product direction. And a wage trajectory of a field that is leveraging it's current cultural cachet to drive a huge recruitment effort.
Once the jig is up, and exposed as just a way to drive down wages, we'll be back to being seen as the hate-worthy nerdy fuckers in the basement. And society will go back to encouraging girls away from the field.
If those are your primary concerns, odds are you'd be more interested in finance or politics.
This is said every single time this comes up. People need to learn how to use a fucking search engine.
http://www.rigzone.com/news/oil_gas/a/135815/API_Study_Getti...
Seriously, the answer is the same as why half of the planet wants to be in tech, money, success, and influence. The general thinking is and has been that you try to fairly populate the mid-top range of jobs, and that's more effective than trying to shoehorn in more women driving dumpsters.