I'm fairly active on various writer/reader forums. I find it's a good way to let people know about my work and to discover new authors whose work I might actually like to read.
An interesting comment that I see coming from a lot of authors is that they say they write short stories "between" novels. Like the short story is an appetizer or palate refresher between main courses. It's a mindset that made me realize that the problem with short stories these days is not the reader, it's the writer.
Personally, I think people are perfectly willing to try out a quality short story. When I do story giveaways, I've never come across a person who says "Oh, sorry, I'm only interested in stories that are over 10,000 words." But I think many writers feel guilty about trying to interest people in a short story.
Consequently, short stories often retain the stigma of being "filler." The author spends most of their time promoting their novel and the short stories are just something that are nice to list off on a resume. They fall by the wayside like they were never written at all.
Perhaps authors feel they're ripping off the reader? There isn't enough quantity to justify the quality? This should not be the case. A quality short story can be just as entertaining as a quality novel. They simply fulfill a different need. Short stories are actual content and every short story author should view them on a plane equal to that of a novel.