When Disney bought Lucasfilm and started on their journey to producing new Star Wars films, one of the first things they announced was that they would be ditching the Star Wars Extended Universe saying that none of it would be canon. This initially pissed a lot of fans off because the Extended Universe is full of great stories and characters.
There are actually many reasons why they decided to drop the Extended Universe and rebrand it into what is now called Star Wars Legends. Lucasfilm originally released a statement explaining why, but Star Wars Story Group member Leland Chee got a little more specific explaining that one reason came down to Chewbacca.
Why Chewbacca, you ask. Because Chewbacca was killed off in the Extended Universe and they wanted to play with that character in the films. While talking with SyFy.com, Chee, who also oversees The Holocron, which is basically Lucasfilm’s official version of Wookieepedia, had this to say:
"For me it came down to simply that we had killed Chewbacca in the Legends — a big moon had fallen on him. Part of that [original decision] was Chewbacca, because he can’t speak and just speaks in growls, he was a challenging character to write for in novels. Publishing had decided they needed to kill somebody, and it was Chewbacca.
"But if you have the opportunity to bring back Chewbacca into a live action film, you’re not gonna deprive fans that. There’s no way that I’d want to do an Episode VII that didn’t have Chewbacca in it and have to explain that Chewbacca had a moon fall on his head. And if we were going to overturn a monumental decision like that, everything else was really just minor in comparison."
That kind of puts things into perspective. The Extended Universe is full of stories, events, and characters that would have made making all the future films a pretty complicated task. Had they actually kept the Extended Universe canon, the filmmakers would have been trapped and limited to the things they could do in telling their stories. Of course, some fans might have rather had the filmmakers boxed in like that. I know some of those fans would have loved to see the portrayal of Luke Skywalker from the Extended Universe rather than what we got in The Last Jedi.
In the end, their decision was obviously made to appease all the Star Wars fans because not all the fans are familiar with the Extended Universe. It was just a headache of explanations that they wanted to avoid. But, then these new films have raised a bunch of questions of their own that the filmmakers are trying to explain anyway.
I think most fans, though, can understand why keeping the Extended Universe canon wouldn't have ultimately worked.