The date palm is one of the oldest cultivated trees and is closely linked with life in Arabia. Its fruit, the date, is sweet, rich in energy and keeps well for a long time without a refrigerator, so travelers crossing the desert often carried it. Dates contain natural sugar, fiber and several minerals. Many people also serve them with coffee as a sign of hospitality. Palms thrive in hot, dry climates but need water at their roots, so date farms are often built near oases or wells. Saudi Arabia is among the largest producers of dates in the world. Every part of the tree has a use: the trunk is used for building, and the leaves are used to make baskets and mats.

Question: Why does the writer say that the trunk and leaves have uses?