I doubt anyone knows.
I imagine the naïve thought process was if you have an association which all parents belong to, all parents will become more involved and then the cadets benefit as mum and dad have an interest.
I would imagine Region and Wing committee types were involved in the process. If they were how soon they forget.
Actually … there is another way of handling this …
Any CivCom who maybe has a reasonable understanding of their responsibilities should know that in Charity Law only the trustees can vary the terms of the constitution.
Because ACP-11 is that constitution, the implementation of the latest revision (i.e. post 2005/6 when the Charities Act was significantly changed in an effort to increase trustee accountability) can only be lawful if adopted by the squadron trustees by vote at a formal meeting of the trustees.
This is known by HQAC who, despite receiving that advise from its legal council and the Charity Commission have bluffed because the level of general understanding at squadron level is poor (oops! back to CivCom training).
So not only does the Association model not fit, it cannot be implemented by just another release of an ACP-11 by HQAC.
I know of some who have taken the current ACP-11 to High Street banks in search of a new account and been refused because the banks legal services advise that the content is in breach of the laws on money laundering. Primarily because the Association model has been given to allow the Association to have unallowable authority and financial access. I think Aries will not get his/her wish on explanation because that would on come from the people who have blundered it to this point.
The difficulty - aware or otherwise - for the many good people who are in CivComs is that ignorance is not bliss since ignorance of the law is no excuse. Uniform volunteers should make up their own minds since the Nuremburg defence was discounted as being legally valid. Not to be rebellious, just to ask questions of HQAC and compare the quality of the answers.