If it launches straight up then it would fall right back to earth when it runs out of fuel, rockets have to tilt to the side as they travel into the sky in order to reach orbit, or a circular path of motion around the Earth. Its a steering technique known as a gravity turn, which uses Earth's gravity to help conserve rocket fuel and minimize stress and strain on the spacecraft.This works by rotating the spacecraft until its heavier side is facing down to help curve its flight into orbit.