No, they haven't. As awesome as novels based on a film franchise are it's a different world (or sandbox if we want to continue down that analogy). People don't just "get" to play in the film sandbox of Star Wars. It's cool of Lucas to have allowed so many books and comics but in the end I'm sure that they were low financial risks (unlike film), reached far less people than the films and nothing he ever felt like he had to follow if he didn't want to.
Oh, now we're restricting the "sandbox" analogy to just refer to film, rather than the whole universe? Because up until now, they were the same thing.
And sorry, but the view that a bazillion dollar franchise should either follow the non-film material or else "make their own sandbox" is just… not realistic for so many reasons, least of all that fans don't get to make the rules. I mean look, I get that people have a strong nostalgic value to many, but thats not enough when a bazillion dollar franchise is on the line. Keep in mind, this is part of a FILM SERIES, not a series of films made from books a'la Harry Potter. There's just zero reason for the people in charge to feel they must follow the novels. Would it be nice? Maybe, but in the end (and I think this is something our current geek/nerd culture really needs to get a grip on) the existence of one thing does not negate the value of the other. Enjoy the books for what they are. Enjoy the movies for what they are. In the end, it will be ok. Maybe not what a group of fans prefer, but thats ok, the thing you love will still be there and probably better than any translation to a new medium would be.
Having respect to the work of everyone who's contributed to the universe so far is a reason. But you're right, that they don't have to do so. Of course, going along that route, they don't have to make "good" movies either, the success of the prequels and movies like those of Micheal Bay have demonstrated that they can make high style, low substance, poorly acted CGI-fests and make money, but I would prefer they don't do that either. Marvel didn't have to take a long term plan of tying together their movies, risking turning viewers off because of too much reliance on other movies, they could have instead focused on more individual movies like what DC did, but I'm glad they did, it paid of.
How is there a loss? Those stories still exist, you don't lose the enjoyment that those stories have brought. I would have liked some of the stuff from the EU to show on screen, because I would love to see what somebody else has imagined for the visual that I have created in my head.
I think that this is hitting some of the same problems that we saw with Eps 1-3, people already had ideas of what "should" happen, instead of what the films are going to say "did" happen. Throughout Lucasfilm/LucasArts and all the peripheral material stuff that has been released over more than 35 years, very little has been made canon that didn't appear in the films first.
It's a loss because some of the the things we like aren't going to be part of the universe anymore, they're not going to be involved in future stories. It's a loss because the material coming out that's labeled "Star Wars" isn't the same as what certain people liked before. I mean, Spider-man's "One More Day" story arc didn't make the years of comics that they retconned not exist anymore in the real world, but to the readers who liked developments from that time period, the continuing comic just isn't telling the same stories that it was prior to that event.
Did Lucas already have a outline or something for 7-9?
Allegedly he had some film treatments that were given to Disney.