User blog comment:GamerPr1ncess/Why are some female gamers underestimated?/@comment-1149295-20100401035241

I haven't met many girls, really. I found a mother of 3 once, but her average K/D ratio was about 0.66

I guess they're rare because girls themselves are rare online, so the proportion that is good is even smaller. No bias here, it's just the ratio in scale.