The music industry has a long and sordid history of ripping off the artists...in the main there's nothing to negotiate because the music publishers own the republishing rights.
Book publishers, contract to publish the book, in one format.
(The same negotiations often have to take place for paperback rights as well, so it's not like this is something new, and is, in the main simple boilerplate contracting with the author, author's agent, or estate) The renegotiations are hard because the publishers are greedy.
Of course all of your basic /. 'intellectual property is theft' technomarxists who never had to make their living off their own intellectual property couldn't be arsed to comprehend this...while musicians can sometimes eke out a living playing live (when they still own their own music, that is), there's not a lot of call for authors to read their books in front of adoring crowds night after night...