MJ, image is important. All of the larger commercial FTOs, and I'm talking commercial not PPL, including OAA, FTE, CTC and Cabair, understand this and insist their instructors wear uniforms, bars included.
Yes, it's all a load of pish, but from a psychological point of view it's important for passengers to see their pilots smartly turned out, and to this end I see no problem with installing that philosophy in student pilots from the very early stages of their training. And following the old adage of monkey see, monkey do, it is, in my opinion, important that instructors lead by example.