They break down those molecules to release the energy for their use. Other creatures called consumers get their energy by eating producers or other consumers and taking their energy rich molecules. Without the struggle to acquire energy and store it there can be no life. Life is always a struggle. Favorable conditions made it possible for life to occur here.
Energy is distributed unevenly throughout the universe.
Our solar system is far out on the galactic rim. We have the right kind of sun. Our planet is the right distance from the sun. Our planet is the right size and density. We have water.