It's not a guy thing, it's a geek thing.
Our local LUG has been in existence for over 6 years but does virtually no advertising. Most of the 200+ members have searched the web for a LUG. And almost all of them are guys, at ages between 15 and 65. Over the past 2 years, there have been 3 women occasionally attending meetings. Everyone has been polite to them and included them in conversations. We would love to have more women join, but our wives and girlfriends aren't interested and would probably frown on us making too much of an effort to recruit specifically women.
The issue is not your standard 'women vs. men' bumping against the glass ceiling. It's the field. Most people in general find what we do horribly boring. But in my experience, of the ones who enjoy it, many more are males than females. A majority of the men I know in the business consider working with computers to be a job and a hobby, and that goes double for FOSS. Honestly, how many women do you know who spend hours and hundreds/thousands of dollars on hardware and/or software, at home, on their own time, because it intrigues them? I know quite a few guys who do.
There are many women in the fields of medicine, politics, science, and the military. But most have made the choice to stay out of the computer business. If you have a plan to change that, and could use our help in a way that won't interfere with our passion for computers, let us know.
Later . . . Jim