Not just for displaying text, but monitors have traditionally updated from left-to-right, top down. If you update the frame buffer in the middle of the screen r

Not just for displaying text, but monitors have traditionally updated from left-to-right, top down. If you update the frame buffer in the middle of the screen refreshing, you end up with screen tearing, which is when the frame that gets drawn has the top of the previous frame, and torn in the middle to display the next frame below.