And women also tend to only commute by bike if the area's safe. Also note, younger demographics prefer the iPhone by just as wide a margin.
I'd say that this is largely due to the way Android's been marketed: just look at the Droid advertisements. The iPhone's been portrayed in a much less gender-specific way.
The iPhone's much better than pink-colored feature phones traditionally marketed to women, while removing a ton of the management necessities associated with a healthy Android phone.
Also, looking at the chart, there's no statistically significant reduction in iPhone interest, it's mainly taking away from "Not sure." I know a ton of women and men with Android phones, but only the guys have strong opinions.