My parents never gave me money unless I worked for it and washing their cars was one of those few things they did pay me to do. I remember always having to scrub bugs off the front, it was the hardest part. I've literally never washed my road cars because its just dust.
What are you confused about? Some cars I've owned cannot go off road, maybe a bumpy dirt road here and there. Other cars I have owned I bought specifically because I needed them to go where there isn't pavement or even a road. They get a lot dirtier and need cleaning just to stay functional.