It is clear that a knowledge of the past is important, so that new mistakes can be made and old ones avoided. Furthermore, failing to understand or know the original reasons for a decision can lead to that decision seeming wrong, and being reversed, allowing the old problem to resurface.
While CotH remembers many things, this memory is enhanced and considerably extended through the archives, which while not providing as much detail as personal memory, are less prone to degrade with time, and give a good description of the issues and solutions tried before.
The archives are also useful for more recent events, allowing patterns and inconsistencies to be noticed, for the benefit of accountability and democracy.