Readers of all ages bought these magazines in huge numbers. Popular classics both in and out of genre fiction that are short story collections include The Adventures of Sherlock Holmes by Arthur Conan Doyle, Foundation by Isaac Asimov, Dubliners by James Joyce, Breakfast at Tiffany's by Truman Capote, The Jungle Book by Rudyard Kipling and Tales of Mystery and Imagination by Edgar Allan Poe. Everyone I know reads short stories and novels indiscriminately. Eight Windows regularly publish story collections. Book reps tell me that booksellers don't like to stock story collections.
Magazine editors prefer to run reviews of novels.
And many publishers are so leery of story collections that on the rare occasions when they still do publish them they often try to pass them off as novels. Perhaps an elegant one-word expression like the French nouvelle or the Italian novella would help matters. Marrow should not have been a novel. In the far future, humans genetically altered to be near-immortal have taken over a gigantic derelict spaceship, larger by far than even giant planets such as Jupiter. Time and space are managed on a scale barely imaginable to planet-bound people who, like the readers, live barely 100 years.