OK, the second reason for the "division line" is....

[CMHCoachNRef]

Originally Posted by SamIAm

The defense bats ball into the backcourt and attempts to go get it. Whistle, deadball, no lay-up for the defense, defense (now offense, gets ball for sideline throw-in).
OR
Defenses stop trying to gain possession and start hitting/swing at the ball, after all what good is tip if it doesn't go in to the BC. Results harder fouls as part of the game, and the introduction of volleyball tactics to basketball.

How are those two "why nots"?

SamIAm,
To clarify, IF the offense touches the ball in the back court after the ball has been tipped into the back court, it would be a back court violation. This is NO DIFFERENT than the play in which the ball is passed directly to the back court by the offense. If the defense gets the ball, they can attack the basket. If the offense touches the ball first, it is a violation. No need for your second scenario to occur as the situation can already occur today when the ball is simply sent into the back court by the offense without a defensive tip. Now, any other "why nots?" (damn punctuations)....