> What I don't understand is the number of restaurants built [...] far away from residential areas

This is probably zoning; in many non-urban places mixed zoning is considered to lower the quality of residential living. So you end up with subdivision mazes without so much as a convenience store in walking range.

> wasn't this because first people decided they wanted to purchase larger amounts of goods per trip

My impression is that it's the other way around: because trips take so long, you maximize the amount you fetch on each.