Another thing is that the once strict observance of taking one’s hat off indoors across US society decades ago may have likely dropped due to hats suddenly falling out of fashion among large groups of men right after WWII when it was once considered almost a mandatory part of one’s dailywear.
This could clearly be seen in pictures which showed most men wearing hats in many settings before the late '40s and after.
One attributed reason for hats suddenly falling out of fashion among males after WWII was that many young men who were conscripted to fight in WWII felt hats reminded them too much of the rigid stifling military environment and its regulations and once discharged, wanted to leave as many vestiges of that environment as far behind them as possible.