This requirement of practicality is one of the important boundaries of Art Deco. Objects must do what they're supposed to do.
The same isn't true of Art Nuveau, which doesn't have the same boundary. Being a pure art, it's didn't use practicality as a touchstone in the same way as Art Deco. Indeed, I am rather convinced that the need for practicality is one of the pressures that caused Art Deco to emerge from Art Nuveau. The practicality of architecture can never be homed to a pure art.
A second issue with a pure art is commissioning the skilled labor to produce it. Architects speak the language of blueprints while fine arts speak the language of drawing. Arguments between artisan and architect delays projects, increases cost, and increases complexity. By eliminating everything that required interpretation by the skilled artisan, the architects were able to greatly reduce the arguments over deliveries while increasing the reliability, meaning that they were better able to bring in projects on time and on budget. This sort of practicality didn't entirely remove all organic design, as sculpture does appear in Art Deco, but it generally appears in places where delays won't halt the entire building project.
Return to: Art Deco 101
Douglas Milewski is a fantasy writer who liked drafting class too much. In his recent artistic struggles to produce art deco for his own covers, he found no internet sites dedicated to the technical underpinnings of the art. Seeing a niche that needed filling, he has documented his hard learned experiences. He doesn't claim that he's right, and would very much appreciate it if someone more competent would save him from his own folly.