Not washing your jeans is part of the hipster craze for vintage and vintage-style denim. The point is to create high contrast fade lines that look cool.
Not washing helps maintain the pattern of creases and wrinkles that naturally form behind the knees and around the front pockets. The peaks and valleys of the wrinkles wear at different rates with the peaks becoming lighter over time. Not washing also keeps the original deep indigo color from fading in the valleys.
The result is dramatic “whisker” and honeycomb patterns standing out against a dark navy background. Some pics here:
https://www.heddels.com/2011/05/fade-types-whiskershige-honeycombs/
No thanks.
I prefer to wear clean clothes.