The problem is that all the infrastructure that cars need (roads, parking lots) makes everything WAY further apart. For example, downtown Houston is literally like 25% parking lots by area. And that's not even counting other car infrastructure like roads. So to some degree, cars are just satisfying a demand for transportation that they themselves create

Denser, less car-centric areas are more economically productive than less dense areas. Car infrastructure prevents density. So I would argue that, at least in some cases, cars decrease economic efficiency