Why step farming is common in hills?

Step farming is more commonly known as terracing. In agriculture, a terrace is a leveled section of a hilly cultivated area, designed as a method of soil conservation to slow or prevent the rapid surface runoff of irrigation water. Often such land is formed into multiple terraces, giving a stepped appearance. The human landscapes of rice cultivation in terraces that follow the natural contours of the escarpments like contour plowing is a classic feature of the island of Bali and the Banaue Rice Terraces in Benguet, Philippines. In Peru, the Inca made use of otherwise unusable slopes by drystone walling to create terraces. This form of land use is prevalent in many countries, and is used for crops requiring a lot of water, such as rice. Terraces are also easier for both mechanical and manual sowing and harvesting than a steep slope would be.