I always wear one - keeps the oil of my clothes and more importantly it has zipped pockets. So it keeps my change and lose bits and bobs contained about my person rather than spread liberally around the airframe. Nothing quite as disconcerting as finding enough lose change to buy a few beers with, sitting in the canopy roof when you are upside down.
Yes, of course my mates, tease me! One, ex RAF wears his green grow bag, with all the squadron patches removed but the velcro attachments remain so that everyone can see what a sky-God he once was!
sNr