In my Council days - pre 2012!- I was on a multi State Transport group in Aussy land.
These wire barriers were discussed, with many of the points of view exppressed here being raised - both for and against.
I remember being shown a video, must have been shot from a helicopter, as it was before the days of drones,
It showed an ocean cliff side road, with the wire barriers between the road and a drop into the ocean.
The video showed a vehicle hit the wire barrier at 60 kph, and an approach angle of 30 deg. The wires 'caught ' the vehicle, and as it slowed it down, at least two thirds of it was "over the edge" - but the tension in the cables dragged it back onto the road surface!   Incredible!  Panel work on the vehicle severely stressed, but it was back on the sealed surface, instead of being 'in the drink'!
Seem to remember thoughts expressed about the effect of the wires on a motorcyclist - similar to being sliced like through a food processor!  And comments such as he was going too fast!
As I said - that was pre 2012!  There are many miles of wire cables wherever one travels these days.