One contribution often mentioned in op-eds etc here is Australia's comparatively lax emission, and non-existent fuel consumption, standards. The idea is that the competitive landscape has been weakened by these factors, making it possible for local manufacturers to avoid the hard work of innovation, and importers to dump old designs unwelcome elsewhere. I don't know enough about the car industry to assess the merit of this, though it would fit the general Australian business (and specifically manufacturing) pattern. There is a kind of comfortable torpor at large here, as most notably described in Donald Horne's famous book.