no one at Paramount cares enough to guide them the way that Lucasfilm guide the Star Wars books.
Actually, that's untrue that no one cares. Paula Block is head of CBS Consumer Products and she helps to guide the licensed ST tie-ins published by Pocket Books, TokyoPop and IDW Publishing. They're just not guided the way Lucasfilm oversees SW stuff - but then, SW tie-in fiction doesn't have as much parental source material as ST.
We are fortunate to have someone who's been a first-generation ST fan since her early years advising the editors of the licensed material and helping to keep them in line with aired, live-action ST (ie. what makes up canonical ST). Paula and her team care a lot, and so do the tie-in editors.
But if the licensed tie-ins "became canon", then every new ST movie or TV show would have to try to track all of these tie-ins, cataloguing their characters, events and tech and acknowledging them. Impossible. As it stands now, the writers of new canonical ST are (and always have been) free to cherrypick what works for them from the licensed fiction. Doing so is why Sulu was called Hikaru in ST VI, and why Kirk's parents are called George Sr and Winona in JJ Abrams' upcoming ST movie.