Worse, they make you wear flammable fancy dress.
Look at the labels in any pilot shop - all polycotton, without any flame retardant.
Nearly as flammable as those horrible yellow jackets.
I turned up for my CPL skill test in my usual natural-fibres "uniform" of flying cotton trousers and cotton polo-neck, my instructor looked at me with horror and quietly asked me if I had "proper" clothes to change into. I didn't, the examiner didn't seem to care and I got a first time pass. I have yet to own a white shirt with eppaullettes, and suspect that I may never do so.
G