Why is the Shinto main sanctuary at ise always built of wood?

The main sanctuary at Ise, known as Ise Jingu, is always built of wood to reflect the Shinto belief in the sacredness of nature and the impermanence of life. Wood, as a natural material, symbolizes purity and is believed to foster a connection between the divine and the earthly. Additionally, the structures are rebuilt every 20 years in a ritual called "Shikinen Sengu," which emphasizes renewal and continuity in Shinto practices, embodying the cycle of life and death. This tradition highlights the importance of maintaining harmony with the environment and the transient nature of existence.