It's a good question -- stains are a reason I assume shirts will be disposable in the end, but it's never been an issue with my jeans, at least not yet over 5 years.
I think it's because my black jeans and dark indigo jeans are dark enough that stains won't show, and my first pair that have turned lighter indigo have so much variation in color and texture across them that yeah, anything you can't wash out just kind of blends in? They basically wind up looking like this (which also shows what they look like after a bunch of darning):
Stains add personality to your jeans. These stains may reflect your work, or your passions, or just unfortunate coffee placement. Whatever it is, it's part of life, your life.
I have had issues with stains while wearing jeans while doing greasy work (particularly on engines) or when I got spray foam on my favorite pair. As long as I avoid grease and chemicals though, my jeans have never displayed any staining.
I think it's because my black jeans and dark indigo jeans are dark enough that stains won't show, and my first pair that have turned lighter indigo have so much variation in color and texture across them that yeah, anything you can't wash out just kind of blends in? They basically wind up looking like this (which also shows what they look like after a bunch of darning):
https://cdn.shopify.com/s/files/1/0028/6132/files/3sixteen-S...
But ultimately, it's been a complete non-issue.