Morgan Freeman wears earrings because sailors wore them to pay for funerals in case they died in foreign lands. Even though he's an airman, he has had a long affinity towards the sea. His own words.
“I always wanted an earring. It has to do with my attachment to the sea. When I was around 35 I was separated from my wife and she said, “I’m going to pierce your ear.” I’m an avid sailor, a dyed-in-the-wool blue-water man.
You know why sailors used to wear a gold earring? It’s enough money to bury you in a foreign country.”
During earlier times sailors used to wear golden/diamond earrings as these were also an incentive for people to search for their corpses and recover them if they died in the sea.