http://www.dailymail.co.uk/sciencetech/article-3049126/Men-competitive-women-Sportsmen-driven-greater-desire-win-regardless-ability-claims-study.html
lol, a daily mail link. It's so bad and untrustworthy I wouldn't wipe my arse on it. You may as well link something from /b
Addressing the topic however I think the reasons are so complex and nuanced you could write a novel on the subject but I'll have a go at it.
I agree accessibility in RTS games is an issue but I believe that it is also an issue for the gaming player base as a whole and not exclusively an issue for women.
I believe culturally there are issues. I feel that playing video games competitively is somewhat frowned upon, it's slowly becoming more accepted and there's more coverage of it in the mainstream media which is great. That straight away is an issue, if the culture as a whole is frowned upon how is a sub culture going to gain any respect from society?
I think women in gaming generally have a tough time. They are subject to a higher level of scrutiny just because of their looks. They are also treated with a high level of suspicion "lol, do you ACTUALLY play video games." It's not a great atmosphere and a lot of women don't want stick around and I don't blame them to be honest.
I don't believe genetics play a part, the problem is that as children you are brought up to behave in a certain way and like certain things. Shockingly it's still frowned upon and considered un-lady like for a woman to like playing video games, let alone competitively. Even in sports being competitive as a woman is somewhat frowned upon culturally, I remember the furor when women started becoming professional boxers for example.
I believe in time things will get better as children don't get pigeon holed to confirm to certain ideals and images as they grow up.