I never think about it much, but I usually don't t wash my jeans until they have some sort of noticeable food stain.
I bring this up, because 's son
has his jeans washed after every use.
I'm thinking it's a generation thing, because the kids now days live sterile lives. They don't play outside anymore and seem to have a problem getting dirty.
I wear my jeans maybe 5 or 6 days a week and maybe I wash them once a month if I'm lucky. I would prefer never to wash them, but dirt, grease and food happen.