Censorship does happen. Stanley Kubrick's last film, Eyes Wide Shut, was censored to avoid an NC-17 rating. You're correct NC-17 movies do get made, but how often can you go to your local cinema and see an NC-17 movie?
I saw it when it came out in the uncensored version and, frankly, the less said about the whole movie the better. Stanley Kubrick made some of the greatest films of all time... and then he made Eyes Wide Shut as an old man because it gave him an excuse to look at boobs for six months.
This is getting off topic, but I don't think it was a bad movie, although certainly not his best. Despite the nudity, the film is strangely un-erotic. I think you are unfair about Kubrick's motives in making the movie. I also think there's much that can be said about the movie, For example: http://www.collativelearning.com/EYES%20WIDE%20SHUT%20analys...
Edited: Terrible grammar.
But the cinema argument is also a bit of a red herring -- your DVD player doesn't refuse to play a DVD of an NC-17 film. Movies have two (or three, if you count TV) vectors for delivery, games do not (in that making different platform versions is often the equivalent to making different movies).