Of course, by this rationale, Wikimedia Commons itself is an unnecessary fork, since all the images in the Commons could be put into Wikipedia itself.
Tsk tsk, being English-centric. Don't you realize that the Italian wikipedia can't refer to an English WP image directly, but has to upload each one to it:WP specifically? We have thousands of cloned images by now. The Commons is actually an anti-fork that will make all the images accessible to all WPs equally.
As the same could be said of Wikispecies (right now we have redundant species information in every language Wikipedia), this is precisely my point.