A discussion forum and a contest are completely different things.
Forums are by their nature exclusive; they address a particular interest. Nikonians is about Nikon; no one's concerned about that. But try discussing film Nikons on there, much less film photography. The reason APUG exists is because most other photo forums discuss digital exclusively or there is so much that analog users have to wade through, while putting up with the occasional snide comments. APUG is about analog; it's in the title.
The Nikon Photo contest is long-established and well respected. It long predates digital. They now choose to exclude a whole class of photographers from their contest- something they never did before. When digital was used by only a few and almost every camera they made was a film camera, they did not exclude images produced by digital cameras. It is not called the Nikon Digital Photo contest, but that is what it has become. They have effectively declared analog to be not photography.