I'm not an ATCer but I believe that ATCOs and ATCAs should wear whatever they want (within reason - no offensive text etc.) as they need to be calm, collected and relaxed/unstressed for when the brown stuff hits the spinny thing and to me that starts with being comfortable. If you aren't comfortable then you can't be as calm and relaxed as you could be. Especially when you have to concentrate for up to 2 hours solid at some units and it could all go mammaries vertical at 1:59 into your stint.