Industrial zones are also a completely different category entirely.
Living in Germany, most German cities do not have anything that is comparable to a U.S. "suburb". Building codes demand a quite high density, even for single family homes for new developments and older developments have the tendency to get denser as the demand for housing in a city rises.
German planning law specifically aims to concentrate development as much as possible, to limit encroachment on agricultural lands and nature. Doesn't always work out, but we have very little of the "urban sprawl" that is so characteristic of U.S. urban planning.