Why did Robert Altman rarely use a traditional shooting script?

Robert Altman rarely used a traditional shooting script because he disdained conventional narratives and preferred an improvisational approach to filmmaking.1

Instead of relying on a rigid script, Altman typically worked from a general concept. He expected his actors to familiarize themselves with the details of the story’s historical period or social milieu and to be prepared to improvise both dialogue and actions. This reliance on chance and collaboration was supported by his development of a repertory group of actors—akin to a traditional theatrical stock company—who were intimately familiar with his unique process.1