I've seen this conversation many times on Reddit, and from what people say I assume there is a regional thing going on on. I'm from a part of the US where toilet stalls do not have massive gaps. There is a big gap at the bottom but too low for anyone to be seeing under unless they are crawling on the floor. Gaps along the sides are quite narrow. 1 cm at most, and nothing anyone is going to be seeing you through unless they are some kind of freak putting their eye right up to it. These stalls are prefab panels you can easily put into a room. The gaps mean ventilation for the room takes care the stalls too.
I assume stalls started this way and became normalized, and in some parts of the country they've gotten sloppier, and sloppier, and normalized these huge gaps I hear people describe but never see.
This might be my bias, but I assume these are the places where everything is a suburban stripmall wasteland, where there are no sidewalks, and where it seems to me the whole environment is increasingly dehumanized.
There a certain ironic cycle there. The cycle you describe of building the suburbs, stores moving in, and people moving in is one part of the cycle. This leads to over-development (in that fucked up car-centric way we have, which leads to traffic congestion etc), and people start moving further out to get away from it. They end up on the edges of it "in the country" with maybe a 40 minute drive for groceries. But then often, the sprawl follows them and their bit of "the country" gets more and more like what they fled.