Virtually all American men wore hats before and for years after WWII. Workin' stiffs wore caps like young Vito and Abbandando did. Bowlers, or "plug hats," generally were signs of someone who was up-and-coming--not yet in the middle class. They started declining ca. 1910. Fedoras were the choice of men who wanted to be taken seriously--and gangsters who were posing as such. A homburg (like the one Michael wore when courting Kay in New Hampshire) was for a banker or a Wall Street type.

I am addicted to hats. I wear a hat even when I go out to fetch the newspaper in the morning. Since I live in AZ, I have a bunch of Western hats for winter, Panamas for summer, and a few "normal" hats with regular brims.