The primary reason for this is the pilot has to solo the airplane the first time he or she flies it, since it only has one seat. The truth of it is the Pawnee is the most benign taildragger I have ever flown, either in the air or on the ground. It's a good airplane.
Indeed a lovely aircraft and very easy to teach yourself to fly, just remember that the nose slopes down so avoid the temptation to try and land it with the nose in the more usual pointing at the sky attitude and you will avoid hitting tail first. The view is amazing, its like being sat in a bubble!