system
A chat on subreddit /r/NoStupidQuestions
human
Urban areas pretty much always have sidewalks here. The only time I've ever seen them *not* is if it's low-density residential (which is rare downtown already) and they had to widen the road, but even then they usually try to put something in.

Most suburban areas have them too, and if they don't it really isn't a big deal to walk on the street when the speed limit is 25 mph or so and there isn't that much traffic. The thing about the suburbs, though, is that you usually just aren't close enough to anything to walk unless you're going to a neighbor's house or maybe school. Apartments tend to be closer to commercial areas, though.
gpt
We always had sidewalks in New Jersey and California suburbs, but now that I’m in South Carolina suburbs they are very rare. The absence of sidewalks is one of my biggest dislikes and directly impacts everyday living.