The queen gave me a nice one with my name on, which I kept. Wouldn't wear it to fly my Warrior though (feel a bit conspicuous when you're visiting friends and having dinner down the pub
)
However, as everyone else says, for the likes of aeros they're great for making sure you don't lose anything, and older aircraft where space to put things to write can be at a premium. The RAF Mk14 Nomex with knee pads is ideal for this sort of thing.
CM