I was reading the following from Noisms and though of my own habits as a Rural GM and my own reasons which very much mirror his own but with complete opposite outcomes.
To me a city is a place where the actions have the least consequences. If you kill a blacksmith in the city you can always go to another blacksmith. If you kill the blacksmith in a rural game, well I hope you like stone weapons. And while a city can swallow players actions and work around them, in a rural game the consequences have real ripple effects. Now that you've killed the blacksmith, what happens to the farm yield when a plough breaks? What do the locals do about you now that you've set off every danger alarm their brains can muster?
To me, if a dead body occurs in a city people may notice, but they don't always care. In a rural game they notice, and they have to care, they depend. The fabric of civilization is much more tenuous and even one cut thread has disastrous effects.
This also might be linked to the ease in which people view rural travel. I read in an encumbrance article where an entire weeks worth of food was listed as the NGR equivalent of 1 dot (the system actually worked really similar to NGR's encumbrance system). Travel to remote locations is hard, and so few people do it.
A rural game to me, will always be my default.