Deformalization of the dress code killed hats. Fedoras and such look great with suits, but they look stupid without them. Worse for the hats’ fate is that suits like fine without hats. So in a day and age when most folks don’t wear suits (last time I did was to be best man about 5 years ago) there’s just plain no reason for hats. I will admit society looked nice back then. By the same token I refuse to put a noose around my neck everyday, so don’t expect my help bringing formal everyday wear back, button down shirts is as much formality as you’re getting out of me.
Case in point, my son flew to a job interview and met with company CEO, CFO, execs wearing his best suit and shoes/sans hat. He said, early in the interview they told him they hope he didn't *always dress like that.* :)