It isn't. What the right word is would probably get me banned from the site....
ctg: I'm not Connavar, but I'll take it upon myself to answer the question ... or what I think your question is. If I am correct, you were asking what makes people from the sff field more qualified than normal screen writers (correct me if I'm wrong). Well, there are a few things:
A.) Many people who have dealt with sff in the visual media have told the same story, whether it be J. Michael Straczynski, Harlan Ellison, Herb Solow, D. C. Fontana, Charles Beaumont, Richard Matheson... pick a name. But the essence of it is that the idea of most producers/directors/screen writers who
aren't from the field have an attitude which can be summed up in one line (which, as I recall, was a direct quote from one such producer): "It's sci-fi; it doesn't have to make sense". (Yet another reason I hate and despise the term "sci-fi" -- or "skiffy", as it has been pronounced: the very terminology degrades the field from something with intellectual integrity to a tasteless, tacky melange of stereotyped imbecilities.)
B.) Science fiction -- at least good science fiction -- requires that you be at least reasonably scientifically literate in order to tell the story. You may tell that story in such a fashion that even a nit who knows next to nothing about science can understand and enjoy it (even the science), but the writer has to be aware of what is going on in the various branches of science, and be at least reasonably familiar with much of the history of science; and the more they are up on the "cutting edge" of what is going on in the various fields, and have a fairly good grounding of the theory and some of its ramifications, the better the science fiction they write is going to be. The bulk of screen writers (like the bulk of most people in any profession except, perhaps, science) are woefully ignorant of such; and even where they are aware, it is generally in the fields of medicine or forensics, where the things they are dealing with are also the sorts of things which make the daily papers.
C.) Most writers within the field are at least reasonably aware of the sorts of stories which have been told already, and tend to steer away from recovering the same ground... or at very least of plagiarizing others ideas. Such is by no means true of the usual screen writers, who deal in little else but rehashings of stories which have been done to death, and still see science fiction as it was 30, 40, or 50 years (or even longer)ago. It tends to be on the level of a screen writer coming to a producer and saying: "I've got this really great idea for a TV movie! Y'see, there's this medical student, and he has this idea of making a man...."
(There is actually a story that someone -- Ellison, if I remember correctly -- tells that isn't all that far from such a scenario. It appears that this head-of-development had one of her writers come to her in a white heat of excitement about this dynamite idea he had, something which was sure to pull 'em in and keep 'em glued to the screen, etc., etc., etc. Excited, she asked him what the idea was. His response: "We do
The Wiz... white!")
At any rate, these are some of the things which make writers from the sff field more qualified. The things which keep them from being qualified largely center around an ignorance of the proper way to write scripts or how to judge what in a script takes how much time onscreen (something very important to know), and how to deal with the visual media... but no few writers in the field have managed the transition, and often quite well. The resulting scripts from such, if you'll compare them to their contemporaries who were not from the field, tend to stand head-and-shoulders (hell, all the way down to the knees!) above their competitors....