If I remember right, this more stringent flight planning requirement for VFR came in with the upgraded air traffic equipment (TAAATS or whatever it was, could well be wrong here) around 2007 or so perhaps?
Even though the air traffickers themselves were very helpful in general (certainly around Cairns where I was flying), the limitations of their new gear meant that if a flight plan wasn't in the system it made a good deal harder for them to flash up a new one off the cuff on the basis of a radio call.
NOTAMS came out to the effect, and in reality, it is now an absolute piece of piss to put a plan in as long as you have access to a computer or smart phone and are willing to take half an hour to learn how to do it, as it appears many are not (unbelievably), but are happy to whinge and bitch.
I would think we all understand that modern computer automation is great in many ways, but there are also downsides in that the old style human scribbling on an information strip and handing it to a controller is not necessarily possible any more, or at least not easily.
I'm far from surprised your mate who didn't put a flight plan in to fly into Canberra (why? couldn't be stuffed, or didn't know how?) got delayed. It clearly says in the AIP that plans should be submitted, and if you don't, expect delays! It's not bloody rocket science, and fair dinkum, takes literally two minutes on your phone to put a plan in.
If for some pressing genuine reason you can't, then I bet the controllers will do their damnedest to help you out.