When meandering across the internet a person can find themselves stumbling across some pretty unique/incredible/amazing/interesting things. The link below is to an article in the Cycle World magazine article by Peter Egan about the History of the Black Leather Jacket. Although not all riders swear by them opting for textile or (omg) spandex/cotton blends, it is a very good read.
Enjoy
History of the Black Leather Jacket