Why Do They Serve Miso Soup with a Lid in Japan but Not in the US?

Image by T.Tseng, Miso soup with crab

“Why do they serve miso soup with a lid in Japan but not in the US?”

When I saw this question posted online, I had to think and search for an answer. Yes, I did grow up in Japan. Yes, I did eat miso soup for almost every Japanese meal at home. But, no, I was unable to come up with an answer.