Why do people find it okay to joke about committing suicide in the workplace?

For context, my manager was talking about how he is not sure if he wants to be a manager anymore, he started having doubts about his decisions and feels like he is stressing over things in the workplace too much and is considering quitting. He was meeting with one of his higher up managers and told him that he might need to transfer to a different role or something. And one of his managers unsurprisingly said he would probably end up becoming unhappy with that role.