Agreed. One wouldn't even have to take any focus away from the plot of the real book to give minor updates on characters at least, which while they're far from really expanding on a character, theyre at least a way of showing that the character remains relevant to the series.
If you have time to visit Atlantis, you have time to spare a paragraph for Rachel to mention "Melissa won the gymnastics competition, isn't that great?" just to show she and Rachel still speak at all since book 2 ended with them maybe or maybe not being on speaking terms.
Or to have Visser Three bark an order to Chapman but call his Yeerk a differen't name, like "Blindiss 622" to show that Iniss blundered enough to be replaced, or indeed moved to a more or less important host (Like Tom, heck I dunno . . . actually I kind of like the idea of Iniss being demoted, given to Tom, then becoming the vicious little beast that Tom's Yeerk was, rising back up through the ranks then stabbing Visser Three/One in the back only to be defeated by Rachel in her final although unwitting vengeance for the pain he caused Melissa . . . fanfic fodder), minor things could have been done but with ghost writers it may have led to continuity errors (Cassie's niece?) so I can see [at least one reason] why they didn't . . .
