It still annoys me that they would yell Touch Down but there is no requirement to Touch the Ball Down.
"When the touchdown was introduced into American football in 1876, it did not award a score; instead, it only allowed the offense the chance to kick for goal by placekick from a spot along a line perpendicular to the goal line and passing through the point where the ball was touched down, or through a process known as a "punt-out", where the attacking team would kick the ball from the point where it was touched down to a teammate."