Throughout much of history, mankind has struggled with transportation issues. Moving people and goods from origin to destination took a great deal of time. Lucky people had horses, but most had to travel by walking. Homes and businesses needed to crowd together for efficiency more than any other reason. This made land in the center of an urban area a premium. This concept still holds true today.
Cities today continue to grow in population, but their boundaries have been permanently set. Creating space in these urban areas requires builders to think vertical rather than horizontal. This is not a new concept, and it was used as far back as the medieval era. Shop keepers had their businesses on the ground floor and their household on the second floor. It garnered them frontage on the small cobbled streets where traffic passed with no travel from home. Modern cities are built on a larger scale, but the idea of combined living space and work space is still used today.