I didn't miss it. If they find it is not as much fun as they thought and they have other options, they drop out.
I'm pretty sure, for example, that women tend to be less concerned about the potential income of their profession.
I wouldn't be surprised if women are on average less antisocial than men, for the simple reason that women are desired by the world. Men wonder how to talk to women, women wonder how to avoid being talked to (great simplifications of course). So computing would on average be less attractive (in the days before facebook anyway).