This has always been my understanding. Why would I state that I could care less about something which I am trying to express that I don't care much about at all?

There's the theory that it implies you could care less, but that would require effort. I don't buy it. It's pretty easy not to care about something, in fact, I think it takes no effort at all. It's not like I'm straining myself by not caring about Joe Smith's new job in northern Minnesota. In fact, I couldn't care less.