I live where wells, septic systems, and propane delivery by truck are the norm. Even the highways in the state were originally privately built and are maintaine

I live where wells, septic systems, and propane delivery by truck are the norm. Even the highways in the state were originally privately built and are maintained largely by tolls. It seems like there would be a tipping range where it would be a toss-up whether it was more efficient to handle these things individually or in bulk, and I wonder how cities make the decision. Like, it would be wildly impractical to run pipes to every house at one density, but equally impractical to drill wells for every occupant at another density. I'm now curious how places decide when it's time to make the switch, and how they do it!