I don't know why, but I find that androgynous people are much easier to draw than strongly-gendered people. So most of my random-person sketches end up that way by default. That or they have beards.
Sometimes, on a rare occasion, I actually feel compelled to sketch out a rough draft of a strip before laying out the vectors. The weird thing is, sometimes I unexpectedly end up with sketchy bits I actually quite like: