Back in the day, it was the polite thing to do to remove your hat while dining in a restaurant.
Not so much anymore. I see guys, especially young guys, with their hats on all the time in restaurants here in Gainesville, Florida.
The custom is quickly fading as a courtesy.
Heck, I remember people dressing up to fly on an Airliner.
Times have changed, but I still blame People Express, the first Cattle Car Airline. LOL