Simple question and the answer is equally as simple: comfort. With a dress you always have to worry about hemline going higher than it should, cross your legs when you sit and can't bend over or do anything that requires you to be physically active ( gym is a good example, obviously). Dresses have a time and a place. Appropriateness of attire is drilled into most GGs as we were growing up, add to that that dresses were reserved for special occasions and not for when I was running around with the neighborhood kids playing and cycling, and you got your answer. Going to the supermarket in my 50s dresses will certainly earn me a few curious looks
