Maybe some of these celebrities had depression? When you're depressed, it takes a lot for you to take care of yourself. Especially when it's severe depression. Other than that, I don't know why they would want to live that way. I'm surprised about James Dean. I never heard that about him before.
Joan washing until she stunk is nonesense. Just washing with soap a few times a day may not even bother your skin. It is an individual thing according to Harvard but soap and water will not make you a rot.