Same reasons if you pocket a ball in an uncalled pocket (as the only ball), it closes a loophole that can cause easy safety shots by simply calling some random pocket and playing it in another one, or by calling a safe and making a ball, then turning over the table without attempting what may be a much harder safety shot. There is also a reasoning that it gets rid of any lucky safes that may be left to the incoming player if they can turn over the table if they don't like it. Even though there is the rule in 8 ball you can do that, 8 ball provides more than one legal ball to contact so playing safe is often harder.
Not picking on you 9ball hanger. I don't play much pocket games but when I did 70's 80's "Call Pocket" was only part of a negotiation, not the norm. I enjoyed the Lack of additional rules beyond you gotta hit the lowest #'d ball 1st, foul the CB = your turn is over, miss the lowest #ball = go sit in your chair, .....
I don't ever remember playing Call 9Ball, but my memory is weakening.
I've said several times here, I think its futile to try to eliminate LUCK from the game. A shooter gets lucky when the shot complied with the rules even though it wasn't the plan, and his opponent is unlucky that happened. On the other hand, an opponent is lucky when by some fluke the shooter is unlucky. A slight kiss for example. The table light came crashing down from the ceiling. A patron walks in front of the shot in perfect time. ............
There's nobody that's played this game more than 1 hour that hasn't benefited or been harmed by luck.
To me, and even if harmed, Luck is part of the FUN OF THE GAME. Extra Fun although Aggravating at times. The aggravation, if you're having fun is another source of fun.
In 2 hours today, I was harmed 6 times from luck. I also inflicted pain 7 times from luck. 4 times I inflicted enhanced pain. = additional billiards after a lucky shot.
I just want to have fun, while at the same time trying to cut my opponents throat, while at the same time he's trying to cut my throat. If he gets lucky... so what!! I will too in time. WHEN THINGS go wrong, so what, we just make a plan to face off again.
Extra rules?? Removes some of the fun and promotes arguing IMO. Not for me.
I'll take my hits no matter the rules.