Ken Griffey Jr. hung out in his dad's MLB clubhouse when he was a little kid, but his dad's hat was too big for him so he turned it around. It became a habit he retained into adulthood, when he became Americans' favorite ballplayer. Fans emulated him, and it's become a style.
Because JFK did not wear a hat to his 1960 inauguration. Men stopped wearing hats over night.Well, maybe so, but I grew up in post WWII SoCal and don't recall ever seeing men wearing hats. In fact, seeing men wearing hats in movies always struck me as odd>