I see a lot of flight schools that require their CFI's to wear the pilot uniform. It’s a lot of the smaller ones too, not just those bigger pilot factories like FSI. Some instructors like it too, as well as the students since it gives them a feeling of authority and respect. They’re only trying to emulate what they want to be.
Personally, I think it's a little too much for some guy riding around in a 152 to wear stripes. One place I know of has the CFI wear 1 stripe, CFII 2 stripes and the MEI 3. I believe the owner felt the outfits gave the school a more professional appearance. Believe it or not, prospective students may psychologically feel better about paying more to attend a flight school that wears this uniform. Just the same, a lot of the instructors really don’t care to wear the uniform and hide it under a jacket.