Why is there no temple in New Jerusalem?

Scripture tells us plainly that in the New Jerusalem John saw no temple, for the Lord God Almighty and the Lamb are the temple of it. God and Jesus Christ are, in themselves, the dwelling place of worship for the city. There is no need for a physical structure because the fullness of God's presence and the presence of the Lamb fill the city completely, so His people have direct access to Him without any building standing between.

This is different from the Millennium, when Christ sits on the throne of God and dwells among the people as King of the whole earth, and He is served day and night in a temple. That service in a temple belongs to the Millennium, not to the New Earth. Once we move into eternity and the new heaven and new earth, that temple service pattern is no longer needed, because on the New Earth there is no temple at all. God Himself, together with the Lamb, becomes the temple, and His people worship Him directly, face to face, forever.