Why do rockets launch vertically before turning?

Rockets initially rise vertically to avoid dense air and nearby structures while gaining altitude quickly. Once safely above the lower atmosphere, they gradually pitch over in a maneuver called a gravity turn. Orbit requires much more sideways speed than upward speed; low Earth orbit needs roughly 7.8 kilometers per second. The vertical portion helps the rocket get above the atmosphere where drag is lower. This is why launches are dramatic straight up at first, then curve over toward the horizon.