The purpose of that little pocket is obvious to any Wild West cowboys or 19th-century gold miners reading this. It's where you kept your pocket watch when jeans were first invented.When Levi Strauss made his first pair of jeans, it was a pretty common problem for the seams of the trousers to tear due to the stress being put on them by the workmen and miners who wore them. The rivets just exist to strengthen the trousers at the most conspicuous spots.