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There's several things going on in this particular example. Firstly, this is a classic early Post Apocalyptic story, with a heavy helping of And Man Grew Proud and Depopulation Bomb. The new society is a False Utopia based on Arcadia, and the suppression of technology and scholarship is a combo of large-scale Technophobia and Persecuted Intellectuals, with the worst of the governing powers being Evil Luddites. The city of Bartorstown is a Hidden Elf Village.
To answer the second part of the question, yep, this is a very common trope in post-apocalyptic fiction, especially in the numerous flavors of The Apunkalypse. (And really Punk fiction in general)
Another similar situation where there isn't a group keeping civilization from rising again is when Scavenger World meets Apocalyptic Logistics: the dispersion is the natural result of there being no industry and infrastructure to support major settlements, and so instead you have smaller settlements scattered around in the Ruins of the Modern Age. (The setting of the Fallout games is a good example.)
Edited by Scorpion451
People living after the collapse of society are only allowed to live in communities smaller than a certain number of buildings or structures to keep from returning to an urbanized state. Does this trope have a name? It appears in Leigh Brackett's novel The Long Tomorrow? Has it been featured in any other works?