Disney is cleaning house and dumping a big chunk of the Star Wars franchise.
The slap-dash, anyone-can-add-to-it nature of the existing Expanded Universe and its tiers is great for detail-oriented fans who want to write a Mary Sue fanfic that includes a perfectly accurate depiction of the seven prime forms of lightsaber combat, but it's absolute poison for Disney.
All of this. I have no doubt there is good stuff in there. I loved Jedi Knight) video games. But as a casual fan who enjoys classic movies, who is aware of all this other stuff, I don't want future movies to have to account for four wire racks of paperbacks.
Marvel has the multiverse as a release valve to jettison nonsense live action movies and cartoons. Disney created a similar mechanism.
I feel for the fans who have invested time and energy. The Star Wars wiki, YouTube, Flickr, etc. are filled with amazing fan work. That's not going away, it's just shifting.
But Star Wars is a business. This seems like a practical step to growing the franchise. Disney/Marvel will continue make top tier movies because they have been willing to branch the canon. They take the good, dump the bad, then mold the stories and characters to fit into a new medium. The fans can keep favorite Extended Universe characters, but now EU lives in its own version of the universe.