The drop kick goes all the way back to the origin of football.
The only way you can get points by way of a kicked ball is if the ball touches the ground, hence the reason there is no tee used for place kicks for field goals and extra points in the NFL, as there is in college football.
Here's another rule yu maynot have heard of, and it involves the kicking game, also.
When a team is receiving a kickoff, or a punt, and calls for a "FAIR CATCH" they are allowed to get a "FREE KICK" from the point of where they caught the ball, by pacekicking, with the ball being held......and if it goes over the cross bar, they get three points.
This can be a good thing if, lets say, there are like just a few seonds left in the half, or the game, you are trailing by 2 points. The other team is punting from their end zone and you call for a fair catch on their 40 yard line, for example. You can then take the FREE KICK from the 40, just like a field goal, with no rush from the opposing team, and if it's good, the points count like a field goal. Same thing on a kickoff if you fair catch it.
It has been done a few times. I saw Parcells do it once. Very few people, including players, are aware of this rule.