Election day in Canada!

Because a vast portion of it is desert. Not Gobi Desert desert, but the type of desert where it's impractical to use agriculture. Grazing is used in some cases but that leads to compaction of the soil and consequent loss (since Australia never experienced mass glaciation in the last ice age, our soils are quite poor in most cases and our rate of loss is much higher than our rate of recharge). And while Australia has a number of aquifers such as the Great Artesian Basin, aquifer water supplies are effectively non-renewable given their slow rate of recharge. The basin's already been tapped dry in various areas in central Queensland and groundwater like it is the only thing that allows towns like Alice Springs to exist. Suffice to say, it can't last forever.

I see. Thank you.