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.
I think this hits the nail on the head!
Certainly there was a time when you could call up Clearance Delivery at Townsville, give a few details, and get a VFR clearance to transit, exit or enter the zone - with minimal delay.
Some time later (years?) such a request was answered with "Do you have details in the system"? If not there would be a delay while they put enough details in the system for it to work. In the last few years the delays seem to have been getting longer and I suspect many, like me on the rare occassions when I want to fly VFR, have reverted to submitting a plan for a VFR flights that need a clearance.
Dr 