What were the main reasons why the incans built a complex system of roads?i don’t understand

The Inca road system was the most extensive and advanced transportation system in pre-Columbian South America. It was about 39,900 kilometres (24,800 mi) long.The construction of the roads required a large expenditure of time and effort. The network was based on two north-south roads with numerous branches] The best known portion of the road system is the Inca Trail to Machu Picchu. Part of the road network was built by cultures that precede the Inca Empire, notably the Wari culture. During the Spanish colonial era, parts of the road system were given the status of Camino Real. In 2014 the road system became a UNESCO World Heritag

The Inca road system was the most extensive and advanced transportation system in pre-Columbian South America. It was about 39,900 kilometres (24,800 mi) long. :242 The construction of the roadsrequired a large expenditure of time and effort.