Because of a feeling of chaos and lostness after World War I.
Details:
Novelist/poet/playwright Gertrude Stein referred to herself and other writers like her as "The Lost Generation." World War I and the aftermath of the war is what gave them a feeling of lostness. The Lost Generation was affected by disillusionment by those came of age during the war years, and began to question traditional values. Some of the writers of the "Lost Generation" were Ernest Hemingway, F. Scott Fitzgerald, and T. S. Eliot - along with Gertrude Stein herself.
