Just to play devil's advocate, that's not quite the same thing because those weren't pre-existing properties that came with certain expectations. Nobody was anticipating that STAR WARS was going to be about somebody other than Luke Skywalker.
But if you picked up a LOGAN'S RUN novel, and found yourself reading about some guy you'd never heard of named "Luke Skywalker," you might be understandably confused . . . or even annoyed. You buy a LOGAN'S RUN novel because you want to read about
those characters and
that world . . ..
(STAR TREK, to be fair, is slightly different in that some readers may be more interested in the overall universe than just "The Adventures of Jean-Luc Picard.")
On a practical level, though, I'm working on my third LIBRARIANS novel now, and I'm absolutely writing about Baird and Stone and Cassanda and Ezekiel and Jenkins because, well, it's a LIBRARIANS novel and anybody who picks up a LIBRARIANS book is going to want read about the characters on the show. And they're going to want the book to feel like an episode of the show, albeit with an unlimited special-effects budget.
A crazy idea, I know.