I think it's because usually the punchline is too long
Starts breakdancing* Thats not as much proof as you think it is
Uncertainty or indifference ' He answered: I don't know and I don't care!'
Sandiego (The first joke I ever made as a kid)
Because it will go right over his head
To get to the other side.
The punchline.
The punchlines are too long.
The punchline is too long.