Just from looking at Meetup.com, I see all kinds of social groups just for women in my metro area, but I never see such things for men. There's social groups for everyone, and social groups just for women, and also social groups just for particular little subgroups (LGBT, [religion], etc.). I think there's something to this.

Another thing I've noticed is how many urban women get their exercise from "classes": barre, yoga, pilates, "orange theory", etc. Go into one of these and you probably won't see a single male there.