I personally believe it's not entirely about males being more likely to be on the spectrum. I think the apparent scarcity is also a reflection of the difficulty many women face getting an accurate diagnosis, and the lack of assistance available to us.
Autism affects males and females differently, yet historically a lot of the research has concentrated on male subjects, so things considered to be stereotypical autistic traits may really be specific to the male autism experience. So females, with our different ways of being autistic, often fly under the radar.
The usual thinking is that there are four autistic males for every one female, but I think key point is that there are four males diagnosed for every one female. Considering that we're still diagnosing people in their 30s, 40s, 50s and beyond who missed out when they were younger because we just didn't know about the condition, we should realise that the diagnosis rate doesn't necessarily reflect the incidence rate.