Denim jeans, a universally loved item, have "miraculous ability to stay clean," according to Stephanie Hegarty of BBC, as she explored the answer to why people wear jeans so much.

According to a test done by Josh Le, a microbiology student at the University of Alberta, a pair of raw denim jeans unwashed for 15 months and the same jeans after washing have almost the same bacterial content.

Le wanted to “show the world that wearing jeans for a period of time isn’t that bad,” according to the university's website.
He even slept in them sometimes.
“You wake up and already have your pants chosen for the day. And I think I gained more friends and had more conversations because of the jeans.”

The university has kindly provided a video of this project:

“It’s encouraging to see that the raw denim movement isn’t dangerous for your health—in my case, at least. It supports the idea that washing your clothes less frequently isn’t as bad—maybe more frequently than 15-month intervals between washes—but maybe less frequently than after every wear,” said Le.

First designed as workwear in the late 19th century America, denim was valued for its fading quality that reflects people's lives over time, said Hegarty. From being a representative of the American West, jeans began to be born as casual wear, reflecting Hollywood's usage of jeans on bad boys in mid-19th century. Symbolizing rebellion and democratization, jeans were then spread to the middle class, youth, and beyond.

"Jeans still have a badge of individuality even if you buy them off the rack," says Paul Trynka, author of Denim: From Cowboys to Catwalks.

"It's not just a three-dimensional material, it's four-dimensional because it changes with time as well. The eternal appeal of jeans is just that they reflect us and they reflect the lives that we've had in them."

Now there is every reason to love them!