I can see this trope has mainly been written to cover the area of military helmets e.g. Soldiers, Knights, Space Marines etc. However there is another significantly large area that this trope should cover, perhaps as a sub-trope. The area I'm referring to is Motorcycle helmets.
My personal bug-bear, being a motorcyclist is that main characters almost never wear full-face helmets, even when they would be appropriate. Full-face helmets are occasionally used for the entrance of a "mysterious stranger", who then removes the helmet to reveal flawless hair. (Dylan from 90210), but normally they are only worn by faceless goons (with tinted visors).
This is usually lampshaded by having the hero steal or commandeer a motorbike during a chase scene (no time for safety.)
Main characters do often wear open-face helmets when riding scooters/mopeds, but only in romantic comedies. Open-face helmets are also occasionally worn by characters riding Harleys, which is somewhat true to life.
But in the real world most motorcyclists, especially those riding high performance sports bike, almost always wear full face helmets.
Sorry for the long post. (I didn't even get started on the fact no-one ever seems to wear motorcycle gloves, even when they wear a helmet.)
It also seems that heroes don't wear hardhats as much as they should.