A human thinks about the smartphone as a whole, drafts it up and builds it [slightly simplifiedly].

Old cities started as settlements, which more and more people moved to. Those people considered things like walking distance. Maybe they "designed" the places to put their homes, but the thing as a whole was in many cases not planned-through.

And even with the cities that were, pedestrian comfort was the main (or one of the main) concern(s).