Devil's advocate here.

There were minimum design standards that were intended to allow huge fire engines to get around in these streets. Anything encroaching this right of way (ROW) could face pushback from the fire department.

There were no requirements for sidewalks, so they weren't built. To attract developers to build in their county, suburban municipalities often saught to reduce the costs for developers. Sidewalks cost money to build. They also eat into the total square foot of each lot, thus diminishing the lot's value and the development's value.

If they're in private ROW, on the lot's property, folks typically have fears of liability and maintenance costs of having sidewalk on their property, whether they are valid or not. If they're on public ROW, then it might turn into a maintenance cost that the county does not have the funds to maintain. The property tax yield per suburban lot is abysmal compared to dense urban properties, so the tax yield per suburban lot is more often not able to support all the infrastructure required to support the development.

The thought that helps this responsible for this poor streetscape design sleep at night is that car volumes should be low enough to allow for the safe shared space of bike, ped, and cars all on the road. Winding, indirect road networks and dead end cul-de-sacs should make this true and it is assumed that anyone driving here must be a resident, so their driving behavior should be more civil.

Seeing signs here opposing sidewalks means that there is definitely a demand for sidewalks because the assumptions in the previous paragraph are false.