It's much easier to design and build on flat ground, especially at scale. Things like road grids make sense, and designs can be spatially translated without cus

It's much easier to design and build on flat ground, especially at scale. Things like road grids make sense, and designs can be spatially translated without custom geotechnical work per site. It also makes it MUCH easier to stage construction equipment and materials. There are people willing to pay the design and construction premiums for a hillside location, but they are not buying developer houses :) Also, the lawns provide a water buffer that's essential for managing stormwater runoff. The more densely paved a city is, the more likely it is to flood catastrophically when storm sewers overload. Which isn't a problem in SF though