[mike_hearn]

Those stories are inspired (somewhat) by the dark ages. Stagnation is kinda the default state of mankind. Look at places like Afghanistan. Other than imported western tech, it's basically a medieval society. Between the fall of the Roman Empire and the middle medieval era, technology didn't progress all that much. Many parts of the world were essentially still peasant societies at the start of the 20th century.

All you really need is a government or society that isn't conducive to technological development, either because they persecute it or because they just don't do anything to protect and encourage it (e.g. no patent system or enforceable trade secrets).

Even today, what we see is that technological progress isn't evenly distributed. Most of it comes out of the USA at the moment, a bit from Europe and China. In the past there's usually been one or two places that were clearly ahead and driving things forward, and it moves around over time.

The other thing that inspires the idea of a permanent medieval society is archaeological narratives about ancient Egypt. If you believe their chronologies (which you may not), then Egyptian society was frozen in time for thousands of years with little or no change in any respect. Not linguistic, not religious, not technological. This is unthinkable today but is what academics would have us believe really happened not so long ago.