You wash your jackets every time you wear them too? How about your baseball caps? your gloves?
I wash my jeans after 2-3 wearings. I wash my workout clothes after each wearing. There is a difference there because I don't workout in my jeans.
I don't get all the people who get so sassy about washing something after one time wearing.
Tshirts, undergarments, exercise clothing - these make sense to wear once.
If someone has a need to wash jeans after one wear, and I mean you perceive some filth, then those people are filthy. I don't know what people do in their clothes, but seeing as I wear boxers, my jeans stay clean when merely sitting around the house, getting errands done, or going out. If they pick up smoke or something (parties, bars, campfire), then they get washed.
I bet these "wash jeans after one day" people are the same ones who wash a bath towel after one use. What a waste of water and detergent. I'm not stingy, I'm simply practical.