It can be therapeutic, that’s been proven. I’ve thought the same thing, only because I’ve read so many personal essays about tragedies. It seems like some need to tell their personal story to feel better/wanted/worthy/acknowledged and don’t actually want to write for a living.
But I also think there are writers who like to share stories with their fellow man in a way that tribes of old used to do, or ones who like to paint but can only do it with words, and others who want to learn all they can about being human and then share that knowledge so that people like me can grow and be better humans. They seem like they have an obligation to do so or else their humanity card gets taken away.