The rivets in your jeans help protect them from wear and tear at high pressure points.
In the 1870s, a tailor named Jacob Davis told Levi Strauss (who owned a dry goods store in San Francisco at the time) how he did it, and they patented the handy trick.
Until about five minutes ago, that little pocket was called a 'change pocket'. It's for keeping your change in.
btw: Levi's used to be a symbol of durability. Levi's used to last like leather. Now, Levi's are no more than a sad, sad excuse for clothing. The scumbag CEO advises people not to wash them because of the wear and tear washing will put them through. I have flannel pajamas more durable than Levi's. Funny tho, that kids keep buying them. smh.