I think it is because it is easier to make a figure from the comics or the video games. Both comics and games are a visual media type, so there is actually one set look for the characters. Whereas for a character from the novels we all may have a different mental picture of each particular character. Settling on a final figure design that will please as many people as possible would be very difficult.
The problem with that as I see it is that Hasbro is missing the opportunity to immortalize in plastic characters which have had a lasting impact on the EU. Take for example Talon Karrde, it took them 13 years to get to making this figure, meanwhile characters just seen in comics in the last year or two and who don't play major roles in the EU segment of the Saga (Mouse and Basso as an example) are already getting figures. Where's the love for Ulic Qel-Droma, Exar Kun, Corran Horn (what, like I wasn't going to add him?
), Ysanne Isard, the Noghri, the Yuuzhan Vong, the Solo kids, etc? I think with the NJO Luke that came in the Evolutions set, a figure which I believe has no visual reference for (someone correct me if I'm wrong), Hasbro could make a litany of novel-based characters based on what reference material is available. And in many cases that material includes visual guides and CCG cards with images of the characters. Just my 2 pennies...
