Returning a 404 status code and displaying an attractive and descriptive status page are not mutually exclusive. If you go to http://www.google.com/unknown, you will get a 404, but you will also see a custom page.
Absolutely, I don't disagree. I'm saying that for most end users, there's no distinction. Status codes are for machines, but if early browsers did something noteworthy with those codes, developers wouldn't have been so quick to dismiss them in a way that is now largely habit.