These architects chose to use their designs as a tool to respond to how quickly things were changing in their world. The early 20th century was quickly turning into a technology-driven, mass-market industrialist society. Many of these architects and designers felt as if people in their society were accomplishing more but were emotionally stunted and less spiritually or creatively fulfilled.
In other words, the design of all furnishings and decorative objects should reflect its intended purpose, and if a furnishing, decor, or decorating detail does not have a practical purpose, then it can be eliminated.
Contemporary style is not born out of a certain era. It changes as time evolves, and can incorporate modern elements. For example, in a few more decades, a new style will be called contemporary because it is what is in style.
As many people strive for simplicity in life—and there's an emphasis on decluttering—perhaps they will be drawn to the modern style because it does seem to simplify everything. That goes along with the design trend of open-concept spaces.