Like @jonsblond said, cities are a bussle of busy people. You have to do it after work hours.
I have met more people in the Boston area afterwork or on the train than I can in rural land.
Rural depends on how rural. there certainly are a few degrees of seperation in rural areas, but if they are bedroom communities, then you may not even know your neighbor. They drive home into their driveway and push the button on the garage and never see them other than that.
It also depends on your personality. If you are more introverted, then you are more than likely to feel comfort and meet people in small towns.
If you are outgoing, it does not matter where you are. Book store, grocery store, gym, etc…...
Interesting question….