Frequently rural, old, or old residential are just unmarked streets (typically barely wide enough for 2 cars) with no sidewalks, or bike lanes, at least where I'm from. In CA everything was built around the car, so I'd assume they thought no one would ever need to walk anywhere, since everything is probably miles away, and cars.
You're not wrong! This is a suburb of Columbia SC that was originally built in the 40s with no sidewalks at all. As it's grown, especially as more university students started living here, they've added sidewalks here and there but only on the streets that get the most traffic. If you see a sidewalk here it usually means you're about to enter a commercial area on the big main street that goes downtown, or you're near a public park
It's more that vehicle traffic on that road is pretty sparse anyway, so sidewalks weren't deemed necessary. Looks like a quiet residential area.
