For very short buzz-around-town stuff, I'll VERY SELDOMLY go without a jacket. Now that I know of NewEnough, I'll probably just get a textile convertible jacket (mesh with removable windbreak lining and armor), and therefore NEVER go without.
Furthermore, the only time I'll without my steel-toe boots and heavy jeans is on the rare occasions I commute to work by bike.
Twelve years ago this month, as a dumb kid right out of high school, I roadrashed my first bike. I got off very lucky, but still have three roadrash scars to keep me humble and remind me of what can happen. I don't care to repeat the experience.