Well actually it is for some. Bicycling magazine.com states various reasons with the top one being for aerodynamics.
Other reasons listed included; improved benefits & pleasure from massage, wound care easier & more effective (as you stated), just looks better, and women like smooth haired men.
Strange lot you cyclists are.
Aerodynamic reasons
Also if it is for stick plaster reasons, then shaving your legs is surely saying you are crap and expect to fall off