They are, actually. George Lucas said that there's basically three levels of canon to Star Wars: the original movies are the main canon, then the extended universe is also canon but is not his personal canon, and then there's fanon, which is non-canon. You seem to be confusing licensed in-universe novels with fanfiction.
For how this relates to TES, Greg Keyes' novels are official canon, but fanfiction is not.
Besides, there's practically no concrete canon to the TES universe. Most of what we know is taken from books written by in-universe authors, who are fallible (and therefore aspects of certain books may be false; the ravings of Mankar Camoran are an excellent example). The lore forum basically exists to debate what in-universe information is true and what isn't.
http://en.wikipedia.org/wiki/Star_Wars_canon
"
When it comes to absolute canon, the real story of Star Wars, you must turn to the films themselves — and only the films. Even novelizations are interpretations of the film, and while they are largely true to George Lucas' vision (he works quite closely with the novel authors), the method in which they are written does allow for some minor differences. The novelizations are written concurrently with the film's production, so variations in detail do creep in from time to time. Nonetheless, they should be regarded as very accurate depictions of the fictional Star Wars movies. "
Also from George Lucas as himself
There are two worlds here," explained Lucas. "
There’s my world, which is the movies, and there’s this other world that has been created, which I say is the parallel universe – the licensing world of the books, games and comic books.
They don’t intrude on my world, which is a select period of time, [but] they do intrude in between the movies. I don’t get too involved in the parallel universe.
There is only 1 REAL Star wars canon. everything else falls into levels of licensed fanon