Why did cuneiform signs become wedge-shaped?

Cuneiform signs became wedge-shaped due to the physical interaction between the writing tool and the medium. As the Sumerian language script evolved during the 3rd millennium BCE, it became increasingly cursive and conventionalized.1

Because clay tablets were the primary writing material, scribes transitioned from using a pointed stick to a blunt stylus. When this stylus was pressed into the soft, wet clay, the slanted edge created distinct, wedge-shaped impressions rather than the curving lines found in earlier pictographic writing. This shift simplified the script, as the wedge-shaped marks were easier to produce and more efficient for administrative record-keeping. The name "cuneiform" itself is derived from the Latin word cuneus, meaning "wedge".123