Originally Posted by
Psydotek
Because it's secksy.
However, i haven't shaved mine for almost a month... Why? It's winter and all i wear is full length pants/tights right now.

The original reason is for leg massaging, and possibly aerodynamics as well (I saw on a aerodynamics chart listing how much time you can save with various stuff like aero helmets wheels skin suits etc, well it said you can save a few seconds over 50km or so... but whatever).
Most people just do it cause everyone else does it, I give myself leg massages and sans hair is much nicer.