rural jobs used to be based around one big local business -- a factory, a coal mine, etc. When it dies, the town dies. Where I grew up, it was an oil refinery closing that did us in. I was raised in the hollowed-out shell of what the town had once been. The roof of our high school leaked when it rained. Cities can make up for the loss of manufacturing jobs with service jobs -- small towns cannot. That model doesn't work below a certain population density.