This only applies for people who have desk jobs and never muster up a sweat. I have to wash my jeans after everytime that I wear them to work since they get dirty and smelly after one day.
It doesn't have to be about jobs.
But work jeans aren't exactly in this category, and that's really understood.
I do agree with Quebert on this one, a rarity for me.
Quality jeans that are meant to be fashionable wear, and not used for working in the mud or grease, should not be abused with wash/dry cycles.
Washing isn't actually so terrible depending on machine settings, drying is what really does a number on jeans. You can hand-wash your jeans with gentle detergent and have the same effect as using something as basic as vinegar. Good gentle detergents in a washing machine shouldn't damage or fade your jeans, if done infrequently to rarely. But they shouldn't be exposed to the dryer unless you are actually intent on hastening the wear cycle, which isn't all that bad of a goal for some jeans, but for good effect, moderation is key.
Ideally, I think this idea also assumes you aren't wearing the same pair of jeans day in and day out, and that you cycle through a few pairs. If you wear a pair daily, it should be cleaned up in some fashion from time to time.
My jeans only get washed when I feel they have really become soiled, or I spill something nasty. I'm not worried about detergents, but I'll hang them up to dry as opposed to using the machine.
I used to wash jeans pretty regularly, but I've tapered back as I've spent more on some nicer jeans with better material. I know for sure that frequent wear + frequent washing for many old Levi, Lee and American Eagle jeans (old standbys growing up) definitely destroyed them over time.