Those tiny copper dots on your pockets
Why Do Jeans Have Rivets?
Jeans rivets look like style details now. They were originally tiny metal reinforcements placed where work pants ripped the fastest.
Quick answer
Pocket corners were the weak point on work pants. They'd rip under the weight of tools, gold, and hard labor. In 1871 a tailor named Jacob Davis started hammering copper rivets into those corners to stop them tearing. It worked so well that he partnered with Levi Strauss, patented the idea in 1873, and created what we now call blue jeans. Modern denim is stronger and doesn't need rivets the way it used to — but they stayed because they still add reinforcement at stress points, and because they've become the visual identity of jeans.

Invented
1871, by Jacob Davis
Patented
1873 with Levi Strauss
Original problem
Pockets tearing on laborers
Still functional?
Partly — mostly tradition now
Next tiny mystery
More things hiding in plain sight

You noticed the tiny pocket
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The small pocket right next to the rivets — another jeans detail with a specific original purpose.

You noticed the backpack patch
What Is the Diamond Patch on Backpacks For?
Another textile detail that looks decorative but was originally functional.

You noticed the extra holes
What Are the Extra Holes on Shoes For?
Another clothing feature most people never use for its intended purpose.