Edward Erfurt wrote:

The most successful and resilient development patterns include a mix of land “uses”—in other words, it allows residential units, offices, retail, restaurants, and the like to exist in close proximity to each other. A variety of uses, regardless of what form they take, creates a natural diversity within a community or neighborhood that meets the daily and weekly needs of residents. This mix also diversifies the economy so that the community is not reliant on one single use of land, but a balance of uses.

For the past 80 years, modern zoning regulations have been written and implemented with almost the sole focus of separating uses. Sometimes, the intention behind this is good—you wouldn’t want a slaughterhouse located right next to a hospital, for example. Other times, however, these regulations have been used to maintain segregation and fuel racism. The eradication of mixed-use development through regulation has resulted in a modern built environment full of single uses of land, segregated by distance. We now have an entire generation that has never experienced, built, or regulated mixed-use development, and thus we have lost it as an art.