Correct me if I'm misrepresenting you here, but are you claiming that the reason that something is invented is always the reason why it continues to be used?
Now it's probably because people don't like "traffic" outside their homes, but basically yes, that's why single-family zoning is still in place. It's extremely silly to want to ban eg corner stores in your neighborhood.
In SF where people have discovered "left-NIMBYism", people will now argue that keeping it is fighting racism, but then if you go into the suburbs they'll still happily argue the original position.
Luckily we don't have to argue about abstractions since we can just go look at land use.
I do think a lot of people want to keep single family zoning because they think it makes their properties more valuable but 1. historical segregation is part of that and 2. if your home price goes up, that only makes you richer as long as you don't want to buy any other homes that've also gone up.
People want single family zoning because they enjoy it more. People wanting single family housing is what makes it valuable not the single family housing itself.
But also people want single family housing because US made apartments are complete shit. They're poorly insulated to heat and sound which means all sorts of unnecessary interaction with your immediate neighbors, making apartment living that much worse, driving the demand of single family housing up.
In SF where people have discovered "left-NIMBYism", people will now argue that keeping it is fighting racism, but then if you go into the suburbs they'll still happily argue the original position.