Skorts (skirts with shorts underneath) are just as easy to run in as shorts or pants, in my experience, because they'll usually have pockets or stitching to keep the skirt part in place. Skirts suck for active wear imo, cuz they usually flap up against your torso when you run if they're short, or tangle around your legs when longer. Can't speak for old timey kilts and whatnot. Pants with pockets will always be my go to. I fully support skirts as fashion wear for everyone though.