Or cyclists like to shave their legs and want an excuse? Or shaved legs gives a psychological boost (more committed), is better for injuries, or when getting physio/massages; or a combination.

Edit:

It's curious to me, because in other areas it seems some degree of surface detail reduces drag (golf balls, aeroplanes too I've heard) - I wonder if short stubble is actually better and that's the effect you get using real legs. That would account for a plastic model only having a small gain.