The problem is it all needs to grow with use and buildings aren't very mobile. You build something with plenty of road/sidewalk at the edge of the city, city grows, traffic increases, land gets expensive so the buildings get as big as possible and split into smaller apartments, street and sidewalk need to grow, there's nowhere to grow, street eats some of the sidewalk since it's more 'necessary'/utilitarian as pedestrians deal with congestion better than cars and western governments are allergic to motorcycles/scooters. Eventually as a middle point a bicycle lane might sprout since it's kind of the mid point of utility and leisure.
But you can't make things obscenely large in the beginning since then if the area doesn't take off you have a huge amount of infrastructure that still needs maintenance and it also feels like a ghost town with less usage.
It was all a lot easier in the 20th century because there wasn't this mix of speed/capability. The cars were shit, horse carriages aren't exactly fast, bicycles were shit... You had | 20hp trabantesque cars - 5hp horse carriage - bicycle - pedestrian |. Now you have | 400 hp cars - faster (e)bicycles - pedestrians | combined with increased safety culture so you need more splittage and more barriers (be it trees, an actual barrier, curvy roads built to slow people down, etc)
But you can't make things obscenely large in the beginning since then if the area doesn't take off you have a huge amount of infrastructure that still needs maintenance and it also feels like a ghost town with less usage.
It was all a lot easier in the 20th century because there wasn't this mix of speed/capability. The cars were shit, horse carriages aren't exactly fast, bicycles were shit... You had | 20hp trabantesque cars - 5hp horse carriage - bicycle - pedestrian |. Now you have | 400 hp cars - faster (e)bicycles - pedestrians | combined with increased safety culture so you need more splittage and more barriers (be it trees, an actual barrier, curvy roads built to slow people down, etc)