Genesis in one paragraph: How it all began. Why is the world so messed up? What is the relationship of God to the world? What is our duty in the world? What is the relation of science and religion? How can we eat animals? These are among the foundational and various questions addressed by this text. It's stories were learned in Sunday School, but it tells a story for adults.
What is the purpose of telling us about the beginning of the world? "Because that's what happened." That would hardly be a purpose worthy of a sacred text. Instead, it tells us who created the world (God) and defines the goodness of that creation and human's place in the original plan of God and human place now in the fallen world.