Sci-Fi short stories are inherently challenging to write

Isaac Asimov fumes in August 1962 when the uninitiated sci-fi reviewers complain about a lack of characterization

Isaac Asimov fumes in August 1962, about the uninitiated reviewers of sci-fi novels, when they complain about a lack of characterization, for they don't know the unique challenge that sci-fi authors face - they have to explain the background/the setting of the story in addition to providing strong character arcs for their cast.

There is a lack of prior shared context for sci-fi stories since they are either set in a futuristic universe or in a different culture in present-day Earth. In both cases, the author needs to find the space in his novel to constantly remind the reader of the difference between the world the author is painting and the world the reader resides in.

And that's why, the short-short-sci-fi-stories are particularly challenging to write. Because within 1000 words, the author not only has to explain the challenges faced by his protagonists but also has to pack a punch and include twists so that the reader can (hopefully) fail at outguessing the author as he reads between his meals.