or maybe if the author is alive there's the chance that they may get po'd over the infringement.
I don't know much about JDS and other than finding his writings a curiosity I wouldn't think more on him but he may just be the kind of author that is not in it for the money and will take offense to "harming" his work...
It may have to do with works in the public domain. The Edgar Rice Burroughs has fought lawsuits since the 1970s to keep Tarzan from going public domain. They went so far as to trademark a literary character (which is bad precedent and invalid but it went through).
Certainly there would be a market for more King of the Apes books.
Yet you can write all of the Huck Finn and Poe mystery sequels that you want and butcher Shakespeare to your English teacher’s malcontent.