Arbogast's Hat
Opening question:
What was the final Hitchcock film in which a male character wore a hat?
I ran the mental processes and came up with : Topaz. 1969. Three from the end.
John Forsythe. As a CIA man. And Roscoe Lee Browne. As a spy of indeterminate origin.
But there was a twist: The 1969 Topaz was set seven years earlier, in 1962, when hats were more prevelant on men. By 1969, they were on their way out.
I think long hair did it. Its hard to wear a hat on a bit fluffy flop of "dry look" male hair. Indeed, there were a number of 70s cop movies that gave off a weird character look: paunchy male cops with long hair and hats plopped on top of the big hair. It didn't look right.
Hitchcock made two seventies movies where the men had long hair: Frenzy and Family Plot.
No hats.
As for his other sixties films, I recall no hats on men in Torn Curtain. I recall a hat on Rod Taylor's head in the SF scene that opens The Birds. Joe Mantell wore a hat at the Tides diner, and some say he's the hatted guy who lights a cigar in gasoline and blows up outside the diner. Did Connery wear a hat in Marnie? Milton Seltzer as the guy who bothered Marnie at the race trick did.
Which brings us backward in time. To Psycho. Who wore a hat?