I don't know. At the same time, it's nice to have that hindsight, for the people involved to be able to talk about, not only the movie itself, but its impact, its reception, etc. Apparently a lot of modern movies do commentary before the movie is even released, so there's no telling whether or not it will even be successful. Not entirely necessary, I guess, but it's nice to have that kind of context as well, as in, "Well, this particular scene is a favorite of most..." or "The fans really decried this scene because..."