Destroying ballots after a board election?

Our nominating committee are reviewing and comparing our bylaws to Robert's Rules of Order for the upcoming election at our June AGM. We see in Robert's that the ballots from the election of the Board of Directors are to be destroyed after the count is taken and the election is finalized. Since our bylaws do not refer to any practice or ruling in this matter; we understand we revert to Robert's for the standard on the procedure.
However this raised a question from this great group of inquisitve individuals as to the why (?) of this practice. Does anyone know the reason the ballots are to be destroyed? What if a recount is called for after the ballots are destroyed and the next AGM is a year away?

That is a good point about Robert's Rules and it is how I have always viewed the relationship between the way our governing document refers to our interaction with Robert's: "Robert's Rules of Order, Current Edition, shall be recognized as authority governing all meetings when not in conflict with the law, the Articles of Incorporation or these Bylaws."
Well, this has allowed me to reread the section in Robert's Rules on the act of electing officers. In particular, 'Counting and Recording the Ballots by Tellers' Committee'. I have found a partial answer to my own question in that we aren't required to destroy the ballots:
"If a recount isn't necessary or requested, the ballots can be destroyed or filed with the secretary for a certain number of days and then destroyed."

What comes up for me frequently with Robert's and our Bylaws (or the Bylaws/governing documents of any organization I am working with) is the intent or history backing the particular rule I am working with. I believe this is why it is important to have continuity in organizations without reinventing the wheel; if that can occur.
When I work with a community organization I stress the importance of procedures manuals and policy manuals in an attempt to alleviate some of this. But where do you put the history or intent down behind bylaw amendments, etc. except in the memories of those involved?