Answer -
John,
Thanks for the question. The reason is because of Rule 4-1-3(b, exception). This rule creates the exception to the ball being declared dead when a player's knee is down touching the ground. The exception applies only to the HOLDER when an offensive player kicks or simulates kicking the ball for a place kick (Field Goal). By rule the ball may be advanced, kicked or passed.
In college football the hold may place his knee on the ground and the ball is not declared dead.
I took some time to answer this question as I wanted to research the history of the rule as to why this is allowed. Through extensive research I could not find the explanation by the rules committee "why" there was an exception other than the obvious.
The holder is a position that holds the ball for a place kick. After receiving the snap it would be illogical to declare the ball dead because the holder's knee was on the ground. It would defeat the purpose of a holder and the purpose of a place kick.
The old football rules declared the ball became dead in player possession when the player was down by contact (much like the current NFL rule). I suspect the origin of this 4-1-3(b) exception dates back to the late 1800's.
I hope this answers your question. Please feel free to follow-up or ask further questions. Additionally it would be appreciated if you would rate this response.
Thanks again,
Victor Winnek
Football Official
http://en.allexperts.com/q/Football-Instruction-2069/Knee-ground.htm
