What’s the use of the tiny pocket inside the larger pocket on a pair of jeans?

This tiny pocket, also known as a watch pocket, was originally designed to hold a pocket watch when jeans were first invented in the 19th century. Back then, pocket watches were common, and this small pocket offered a safe place to store them. Nowadays, even though pocket watches are rare, the pocket is still included as a traditional feature. It can store small items like coins, USB drives, or even a lighter.