It goes a little beyond fashion and cultural norms. It is part of the human psyche that obediance to authority is much increased if the person in authority is wearing a uniform cap (Yes, someone actually researched it).
In pre 9/11 times, when it was necessary for the Captain to proceed to the cabin to control unruly passenger/s, our company's Operations Manual listed as Item #1 -
Put on your hat.
Try a small private experiment. If your company's procedures allow it, take a stroll through the cabin with your hat off. A few people will give an interested glance. Now, try it with your hat on, you will have their full attention.
I kid thee not!
Regards,
Old Smokey