I don't know about you two, but ...

1) I don't have hair on my elbows, and only very light, thin hair on my arms.

2) I have only scraped up my elbow once (right elbow, still have the scar), but I've scraped up my left left knee twice, quite badly, in 2004 and 2007. I'd have two large scars, but they're right on top of each other ... and I've just re-scraped the scar area in a non-cycling-related fall. I also scraped both legs from the knees right down to the ankles on that 2007 crash. Fortunately the depth of those scrapes wasn't enough to leave much in the way of scarring, but I was glad I shaved before the ride!