Why do we need the infrastructure of cities to survive? Because we are too many people to live off the land like our ancestors were able to do. Also, we lack th

Why do we need the infrastructure of cities to survive? Because we are too many people to live off the land like our ancestors were able to do. Also, we lack the knowledge to be self-sustaining. Why are pre-industrial cities not a good model, i.e. why didn't pre-industrial cities provide the protection we have knowadays? Exactly because we were able to leave out pre-industrial cities in times of turmoil. Since we cannot rely on our self-sufficiency to survive, we need to maintain infrastructure to keep us alive. Maintaining infrastructure is cheapest when the infrastructure is used by as many people as possible. Having a widely distributed population requiring well maintained, widely distributed infrastructure will not be possible.