It used to be common knowledge that people behaved differently, depending upon what they wore. There were school clothes, play clothes, and dress-up/party/church clothes for children and comparable ones for adults. And this was a time,when people did NOT own ,many clothes (even those in the upper middle class and above !); unlike today.
My best clothes are those that last the longest. They are stiched securely and made of fabric that doesn't tear easily. In terms of pants, this means jeans. I've never, ever had a pair of dress pants that would stay in good condition as long as a pair of jeans, assuming equal duration of wear.