To play Devil's advocate (which sounds highly ironic in this context), the god of the Bible ("YHWY," "The Lord," whatever...) doesn't "need" anything. We often confuse the words "need" and "want" (aka desire, crave). So I think a better way to present the question is "Why does God want our worship?" or simply "Why?" as in to question the whole point of everything.
It really is this elephant in the room. An all-powerful, all-knowing disembodied consciousness decides to create other consciousnesses, some astral plane referred to as "heaven", and the universe. Why? It doesn't need anything. That question is never answered.