It is in the universities interests to advertise that their IT degrees include ACS accreditation (despite no Australian IT employers I know of giving a damn about it) and it is in the interest of ACS for the university to keep paying the exorbitant fees. If anything, I feel that ACS accrediation is detrimental to the students as it requires the university to include such useful courses as "Ethics for the IT Professional" in their degrees. While being ethical is obviously important to any professional, this is time that could be spent learning real skills instead.
While I can understand that a professional body would want to ensure that people acted ethically and in good faith, I would think that it would be wiser to ensure that people graduating from technical, engineering related, and detail oriented degrees were just that. That way having an ACS seal of approval on a degree would carry some sort of weight towards the technical quality of the person, and hence would actually mean something.
Maybe it's the spaces and people I work with, but no one that I have worked with is actually a member of the ACS, despite being in industry for almost a decade.
They need to show that there's some Code that could be made enforceable by legislation. It's part of the bigger plan to lever the ACS into the same role that the law societies or the AMA enjoy.
I also just looked at the website, and all of the membership levels look like rankings in a guild system to me. Spend your time, pay more money, rise in ranks. Protectionism at its finest, and even though I'm heavily a software developer, I'm still against this burden.
Basically software liability is just rolled up into the relevant market. Writing facebook games? It doesn't really matter to society if you get it a bit wrong. Writing pacemaker software? Then you're governed by medical device regulations.
Software's application to problems are so varied, so wide, that it's insensible to apply a single liability scheme to it.
The wide range of software that can be written precludes a standard measure of risk and liability, hence it eliminates the need for an (software) industry wide accreditation body.
Plus I've always found smaller more local meetups to be a better way of interacting with a specific development community.
It seems the lower down the qualification chain you go, the more importance is placed on giving you fancy certificates. ACS membership is one of those things.
Of the basic form:
"Here is the Code. Read it some time."