part of the reason this is so bad in the USA is indeed what OP named, the concept of 'legibility', as explained in 'seeing like a state'.
In the case of the USA, though, another 'lens' on the legibility is that overall the people making the laws were neurotically concerned with keeping black people away from white people and enforcing segregation.
'separating uses' was a good way to also 'separate users', and a little barely-that-creative law-writing lets someone keep black people quite removed from the white people.
I found a document from 1922 that is upstream of all american zoning codes - it's what got ratified in Euclid v. Ambler circa 1926.
It's explicit goal was:
"To maintain harmonious relations between the races, care has been given to ensure adequate separation between the two, with room to grow without encroaching on the other"
"The ordinary two or three story store and dwelling building is not a desirable type of construction from a public stand point. The regulations as applied will tend to reduce the number of flats that would otherwise be located over stores."
So - there it is. The goal of American zoning was, in part, to eliminate 'the ordinary two or three story store and dwelling building'.
"Unlivable" isn't normally used in the literal sense. A nasty, unheated, rat-infested apartment, for instance, can be said to be "unlivable", though it really is possible to live there if you're desperate enough.
In the case of the USA, though, another 'lens' on the legibility is that overall the people making the laws were neurotically concerned with keeping black people away from white people and enforcing segregation.
'separating uses' was a good way to also 'separate users', and a little barely-that-creative law-writing lets someone keep black people quite removed from the white people.
I found a document from 1922 that is upstream of all american zoning codes - it's what got ratified in Euclid v. Ambler circa 1926.
It's explicit goal was:
"To maintain harmonious relations between the races, care has been given to ensure adequate separation between the two, with room to grow without encroaching on the other"
The race-based zoning designations are gold:
"R1 - white, R2 - colored, R3 - undecided"
Here's a deep link straight to that portion of the document: https://josh.works/full-copy-of-1922-atlanta-zone-plan#race-...
Oh, it also says:
"The ordinary two or three story store and dwelling building is not a desirable type of construction from a public stand point. The regulations as applied will tend to reduce the number of flats that would otherwise be located over stores."
So - there it is. The goal of American zoning was, in part, to eliminate 'the ordinary two or three story store and dwelling building'.