Pocket watches in the 19th and early 20th century had chains attached to them. American cowboys, who were among the first to wear jeans, generally used to keep their pocket watches in their waistcoats. So to keep them safe from damage, Levi Strauss initiated this trend of tiny pocket in jeans in which the watches could be kept. It became a hit all over the world.
So now you know how the tiny pocket has remained a great service provider.