purely because they look cool.
if you really want to cool your brakes then run some ducting from the front of your car to your wheel wells.
if CD/S brakes were the bees knees then you would see them on every performance car and there wouldnt even be an argument. but you just see them on riced out civics and shit… f1 cars dont use em, nascar doesnt use em, 24 hours of le mans doesn use them… hmmmm…