Sometimes, more often than not when in the shop forging, and covered in sweat. A shirt just adds weight when it's 130F in your work environment. I don't think I would go without shirt kilted out in public, though it has happened at a blacksmith conference once. Pretty mature audience at such gatherings though, in age and attitude both.

Part of the reason I wear the kilt is to look decent if out in public. And not wear trousers.