This is a massing rule—staggered setbacks—that makes sense in a very specific (and extreme) design context: the skyscraper canyons of Lower Manhattan. And yet it's now mindlessly enforced across North America. https://twitter.com/Sean_Hertel/status/1335263068444614656

In the 1916 code, setbacks in the strictest height district wouldn't even kick in until ~50 to ~80 feet, depending on the street width. Today we just apply it to dopey three plus story midrise buildings, regardless of actual light and air considerations.

These examples from near me in LA always crack me up. Can't say for certain whether it's a zoning thing, but I assume so, since it's consistent among new construction. It should go without saying that the effect at this scale is purely aesthetic, serving no light and air purpose.