We need to remember that joining on base was accepted and common practice for decades. As far as I know there was no history of accidents that caused CASA to change. I believe it came out of a risk management meeting with a bunch of faceless Canberra bureaucrats.
In the "good old days" we seemed to get along happily without transponders, higher traffic movements and a greater diversity of aircraft in the circuit. I agree with Tony Kern when he talks about a need recognise that safety is more to do with taking personal responsibility rather than looking for the system to save us.