Why do adults steal lunches from each other at work?

I was reading this article about a woman and her husband who got revenge on this guy who stole the woman’s lunch at work. It reminded me of an episode of Friends I saw, where one of the characters kept getting his lunch stolen. I did some searches on Google and found all sorts of things. I saw several tactics for revenge and several complaints about lunch thieves.

Why is this a thing? Especially in offices with professional adults? Why would people just grab lunches that didn’t belong to them and eat them?