I'm probably not going to bother putting lipstick on for a run, but why the hell shouldn't I?
Can't think of any reason. I might wonder, if I saw someone wearing a great deal of eye makeup while running, if they weren't risking having the stuff get into their eyes when they worked up a sweat, but they probably know more about waterproof and sweatproof stuff than I do,
I can think of a very good reason to put SOMETHING on my lips when running: preventing chapped lips. Why should it matter whether it's decorative or not?