Euclidian use-based zoning has been the law of essentially every city in the US beginning about a hundred years ago until the rise of form-based codes like the SmartCode mandates that uses be separated: housing into subdivisions, retail into strip centers & shopping malls, and offices into office parks. This means that you have to drive pretty much anywhere. So if you look at the gross density, just the space required for larger streets, collectors, arterials, and expressways guarantees a substantially less compact city. This is exacerbated by the large setbacks required by those ordinances.

This was celebrated by the architects; Frank Lloyd Wright's Broadacre City celebrated the ideal of every home sitting on an acre of land. Contrast that with the Tuscan town of Pienza, Italy, which sits on a bit over 11 acres of land and which contains over 2,000 residents. Just looking at the numbers, Americans would think it must be some horrible slum. But it's such a fabulous place that it attracts close to a million visitors a year, if I recall correctly. It would be completely illegal to build Pienza in countless American towns and cities, and on many counts. In reality, Pienza would probably violate close to 90% of the conditions in a conventional Euclidian code.

Regulated out of existence.