First off, there's nothing un-manly about shaving your legs. It doesn't change your sexual orientation. It doesn't make you less of a man. Male cyclists and speed skaters make up lots of reasons why they shave. We say stuff like "it's better for massage" (I haven't had a massage in over a year), "it keeps hair out of your road rash when you crash (possibly true), or "it's more aerodynamic/faster" (which it is, according to the Specialized Win Tunnel). Maybe all of that is true, but I think most of us just like the way it looks and feels, but we're too afraid to actually admit that.
I get pretty lazy in the winter time and rarely shave my legs. Most of the time my legs are covered with tights or knee warmers, so the extra few minutes of shower time isn't really worth it. Every couple weeks I'll just trim them down with electronic clippers and call it good.
I know it's all placebo, but as soon as I shave my legs in the spring I automatically feel like a bike racer again. It's like putting on race wheels. When you look the part, something internal just clicks and you feel the part.