Writing about post-apocalyptic worlds has a long and fruitful history in science fiction -- so long and fruitful that I am real tired of them. When I sense post-apocalypse my first reaction is, "<sigh> Next." But the popularity of post-apocalypse means mine is not the typical reaction of the typical reader. This enduring quality means that it is playing to instinctive thinking -- "let your heart be your guide"-thinking.
Why is it popular?
One reason is that it is simple. Readers are very familiar with the concept so the writer doesn't have to take up a lot of words explaining what the world is like. Compare the following...
John walked to the top of the rise. He looked across the dusty ruin that used to be a town. He shifted his pack, double checked his shouldered rifle, and continued his walk for what used to be the center of his home town. His journey was nearly finished.
...to the start of Tolkien's "Followship of the Ring". Tolkien starts with a birthday party and spends three chapters just introducing us to hobbits and how they live.
Another attraction is that life is cheap, meaning the rituals surrounding action-style violence are minimal.
Three men stepped out from behind a ruined wall. They were big; they smelled bad; they were carrying clubs. They circled John.
The leader spat, then said, "Ah recon you wants to give us all yur stuff."
"And I recons you all want to be dead," said John as he whipped out his pistol and fired three shots. One of the thugs only staggered, he didn't fall instantly. John put a bullet into his forehead. "Damn, I'm getting sloppy." he said as he reloaded, put the pistol away, and continued walking.
No police, no reporters, no forms to fill out. Real simple, on with the story.
Another element of post-apocalypse is tragedy and redemption. Mankind has failed. That is sad. But there is still hope, there will be some personal act that indicates mankind can survive and can grow again.
John made it to the town square. The walls of the church next to it were no longer standing, but a few of the sturdier headstones in the graveyard beyond survived. John walked to one of these, a particular one, and pulled a package out of his backpack.
He knelt and said, "Ma, I've brought Little Nipper back to be with ya. Some crazy ass foreigner zombie had a taste for dog brains, but I brought the rest of him back. Rest in peace. I still love ya..." John tensed a little as he thought of something and fingered his rifle, "As long as you stay put, that is!" Ma continued to rest easy.
He put on his pack again, and started the journey home.
So post-apocalypse is easy to write about, life is simple, action is simple, and it resonates well with tragedy and hope. It's also very familiar. Note that what I've done above is told a complete story in just one third of a page. I can do this because the background is so familiar to readers there's much I can leave unsaid.
There's a lot going for this format... but not enough to sustain thousands and thousands of similar stories. Time to move on. And speaking of moving on, if you'd like to see a Technofiction version of John's story -- honoring a parent in their grave -- check out my story "Wilderness 2053" in Tips for Tailoring Spacetime Fabric Vol. 2. See how putting this story theme in a rich world setting changes it.