According to Active.com, there are many reasons runners, as well as bikers and swimmers, shave their legs. One of the top reasons that athletes shave their legs is to allow wounds, such as road rash, to heal more quickly.
Another important benefit that runners and other athletes derive from their shaving practices is that after-exercise massages work better on hairless skin. When a trainer or massage therapist applies lotion to hairy legs, it creates a sticky mess. By contrast, lotions go on smooth skin very easily. Many people suspect that shaving their legs reduces wind resistance. However, the amount of wind resistance produced by leg hair is negligible.