Sure, it's not required to build _some_ houses, but it's required for scale. Backyard forges are OK if you have few hundred million people, most of them in far

Sure, it's not required to build _some_ houses, but it's required for scale. Backyard forges are OK if you have few hundred million people, most of them in farming, with most families living in a house with a a single room. But you cannot build New York on without large factories.