Forget R, how is this rated PG even now?
The print of the movie I watched had a PG rating. In the film, there is explicit drug use, explicit language (I recall that one use of the word that starts with 'f' is an automatic PG-13 rating), nudity, and very mature content -- prostitution, drug use in general, etc.
I would think the extended shots of needles being inserted into veins is enough for PG-13 by itself, let alone the above.
I mean, "Midnight Cowboy" was rated X on release and a few years reduced down to R, and that was almost entirely for the subject matter alone. I think that the subject matter in this film is just as intense.
Am I alone in this or are others confused? For what it's worth, I'm not railing against the movie in any way. I think it is a very good film and that the content of the film is important in a way as it shows the audience what drug addiction can do.