DoPo said:
No, not really. It's a theme that is explored by relatively a lot of cyberpunk fiction, but it is not a requirement. It makes as much sense as saying "Fantasy is about elves". Elves are there because Tolkien had them, corporations are there because Gibson had them. Cyberpunk, by its very name, is about technology and how it leads to, or perhaps rather helps with, the breakdown of society. That's it "technology" and "breakdown", it's what "cyber" and "punk" refer to in the name.
That's not true in either case. "Cyber" refers to computerization and virtual (digital) reality, while "punk" refers to a humanist rebellion against the powers that be, which due to the power of the "cyber" is necessarily related to control over digital reality. All cyberpunk is about the dehumanizing and destructive effects of private crony control of computerization and digital reality (and sci-fi extensions of such) and a humanist counter-revolution (sometimes successful).
The term "cyberpunk" is related to computerization specifically, which became an unstoppable force in the 1990s.
The real background for cyberpunk, although it's often not noted in the works themselves, is the dying earth. That's the motivating factor for the destruction of humanity - since the earth won't be capable of supporting billions of humans during the 21st century (assuming current projections continue), human beings no longer have value as living entities, moreso as entirely exploited agents, corpses, or new types of beings transformed by the emerging digital reality. Since there's no future for humanity, there's no reason to maintain humans AS humans, so transgressive techno-spiritualism resulting in post-humanism is the result.
The Hacker movement combined with the dying earth which brought us computerization (and cyberpunk) seeks a solution by going to the deepest recesses of the system itself, just as the solution in Cabin in the Woods was to explore the very workings of the system. That's why William Gibson protagonists are always "leet techno agents" or "leet cultural agents" - they are "post-humans" always entirely embedded into the system itself, regardless of their motivations.
Cyberpunk and hacker culture itself is post-apocalyptic - the idea is that the human apocalypse has already happened, we live in the wreckage, and we seek a new way forward not through the old ideas of religion and community but through technology and post-humanism.