To clarify what others are saying, the design and layouts are repeated, but done in situ. So especially in a new house/neighborhood you’ll have a neighborhood with maybe 1-4 variations (possibly also mirrored versions of them), but each was made on the spot with a mostly standardized lot. Then over time some will slowly be modified and they’ll all get their owners’ touches to them.

It’s very much an industrial process in the suburbs starting after the world wars.