Let me add to your cynicism, Peter, by arguing that there has been many completed, successful projects. They just happen to be stories that are posted on Worldbuilding SE as questions and are thus licensed under CC-BY-SA.
Since I can only offer my own contributions as proof of this happening, I'll offer this one - my answer to My Program is designed to be resistant to malware and DOS attacks and isn't letting me turn it off. What do I do?. The OP pretended to be a person who developed a "rogue" program, while I RPed as the "rogue" program itself. I didn't intend for my answer to somehow inspire some glorious plotline, because my answer was already part of the story (with the OP providing the introduction and me providing the conclusion). A clear, consistent narrative already exist and has been published. Not really much point to flesh out the concept or characterization afterwards (unless you really want to know whether the "rogue AI/programmer" tag-team actually works out).
In fact, one could easily take that whole question thread and reframe it as its own short story. The OPer talks to a defense committee, and each person on that committee provides his/her advice on the topic, with the statement from the "rogue" program coming as the epilogue. You only simply need to add a few connector words (Then, the great Cyber-Ethics Professor M i ech said...) to tie all the answers together. There are many world-building Q&As where the OPer pretends to be a main character in his/her world. All those Q&As can be easily converted into glorious short stories. That'd be a good way of boosting the number of "published fiction" stories, and anybody can take on this task. After all, all content on StackExchange is licensed under CC-BY-SA. Anyone can reuse it so long as you provide attribution and you provide the same license.
Disclosure: I also wrote a Q&A pretending to be a main character in my world...though in my defense, I actually did intend to build a narrative using advice from that question. But at the same time, it's very easy to reframe the question as a short story about a CEO begging his corporate board for advice. Torisuda's answer along with Ringo_St R's rebuttal would be a decent subplot. In fact, Torisuda's answer could serve as a decent standalone narrative. No fleshing out required.