I think the USMC has it right and hard for me to say that
USMC Camo Cover - 1980's
These covers are worn ONLY by USMC pilots. The purpose is to signify that the pilot was a "ground pounder" first. Marine Corps pilots must serve at least a year in the infantry before they are eligible to fly.
It also shows that their first job is to provide support to the troops on the ground.
I don't think this is an accurate statement.