Hats!

[tomustang]

Fashion history 101.0:
The demise of gentlemen wearing hats occurred about the time JFK became a public immage. Whereas Eisenhower almost always wore a hat when outdoors, JFK never wore a hat. So...it became fashionable for men to not wear hats. And speaking of men wearing suits and ties, my father and mother would always "dress up" even when just going to visit a friend, or even just go to the movies.

Very good observation. Is that timeline true for europe as well? I am also curious as to why hats in the first place. I can think of a few possibilities: No indoor plumbing and infrequent scalp hygiene; sun/glare protection pre-sunglasses. But was going out without a hat considered taboo, or was it just considered foolish?

It is a tool. It's a hand powered fan, sunblocker, head cooler or head warmer, your worth without telling anyone, it can also be a bag.

I wouldn't doubt hats were first made for protection, just like something to protect your feet. They probably started off as a rag to cover the head and evolved into something with a brim to cover sunlight.