One thing that I noticed is the prevalence of denim in work and very casual environments.
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Unlike today, denim was meant purely to be worn when the wearer was going to get down to the nitty gritty. Rarely was denim ever 'dressed up' with more formal accoutrements (sports coat, nice shoes, dressy shirt, etc.) like it often is today. One unusual exception to this were farmers who liked to wear worn out suit jackets over their denim overalls, though I doubt they were trying to 'dress up' by wearing this combo.
I like to keep denim where it was originally meant to be: at work and extreme play.