Australia has a 90% urbanisation rate, which is one of the highest of all non-city-state nations[1], though our cities are quite spread out. It's a total myth that we're all comfortable in the Outback, one that most of us seem to believe ourselves. We're suburbanites and urbanites, as a rule of thumb.
Regarding the costs, laying new fiber is more expensive than not laying new copper, but the copper circuits we have are so old that maintenance costs are ballooning. There's not really a serious cost argument for or against the NBN, it's really about politics.
copper is for providing DSL to that cattle ranch 100 miles from civilization
DSL doesn't stretch that far, by an order of magnitude (perhaps two orders) :)
> which is one of the highest of all non-city-state nations
Including all nations, it only drops to 17th - still in the top 10%.
.so doesn't have much for resources other than pirates and hungry people, so if they're going to have to import everything, may as well be the new stuff.
Another way to look at .au vs .so is .au is very sparsely populated other than coasts so "most people" will likely end up using wireless for everything, and copper only in unusual areas, and perhaps not so in .so where a very substantial fiber investment might be required to pepper the entire country with wireless towers.
Inherently fiber "should be" much cheaper tech that copper, but due to existing infrastructure and historical economic conditions, its currently applied the other way around, so expensive fiber is for big cities and cell towers, but copper is for providing DSL to that cattle ranch 100 miles from civilization. If .so only serves the rich in the big cities, they have no use for copper to feed the rural poor who won't be getting service, as a theoretical example.