"http://www.polyvore.com/cgi/img-thing?.out=jpg&size=l&tid=46293285"
My point stands.
@Oct: it could be said about any sport:
1. Rugby has the same idea.
2. Cricket: the idea of hitting a ball with a stick to land outside of an oval laid out by a rope before running back and forth between 2 other sticks
3. Baseball: the idea of hitting a ball with a stick directly in front of you before running in a circle
4. Golf: hitting a ball towards a hole (ok that atleast makes some sense)
5. Hockey: Get a disk into the back of a net and kill people in order to do so
6. Soccer: Kick a ball into the back of a net.
etc. etc.
"What's it for?"
Well once you get the touchdown you have to choices, kicking the ball like 15 yards, which your right is incredibly easy and so most accept it as guarenteed.
The alternative is to make a run play which gives you 2

, but a much larger chance of failure, it rarely happens but your team is down 2

with a minute left in the game except that run to force the over time.