I think that very often through a long period of time there's just a general culture of secrecy that pervades many levels of government and a notion that individuals requesting information should get only the information that they're specifically and legitimately entitled to, and nothing more.
So a lot of effort goes into making sure that only that limited subset of information is released, which I think is contrary to the general principles in the act. Certainly the preamble sets out that the default position has to be openness and access, but when it's mechanically applied in a very rigorous way, the culture kind of gets twisted around so it's actually the opposite of what was intended.