You don't hear much about Douglas Duer these days but the once popular illustrator painted for books and magazines from 1912 until the Great Depression.
A student of Howard Pyle, Duer worked for magazines such as the Saturday Evening Post, Collier's and Red Book, and illustrated covers for Zane Grey novels such as Riders of the Purple Sage. During the Depression Duer's illustration work dried up so he found work painting murals for the WPA. Later he made a living doing advertising work and greeting cards.
It's difficult to say why a whole flock of artists during this period were attracted to such a clean, artificial look, but artists such as Enoch Bolles, Tamara de Lempicka, Thomas Hart Benton and Dean Cornwell all painted with a similar style. They took the idealized flesh of Ingres and Bouguereau and converted it into injection molded plastic.
Personally, I suspect this style became popular because these artists worked in an era where science, industrialization and mass production held out the prospect of designing our own environments. In a man made world, everything became cleaner and more streamlined-- polished steel and aerodynamic engineering eclipsed the unruly knots and warts of organic nature. This aesthetic seemed to apply to people as well.