Here is a list of countries that have a bigger population than Australia and won’t have hosted summer Olympics between 2000 and 2032:
Spain, Italy, Germany, Netherlands, Poland, South Korea, Russia, Canada, India, Mexico, Turkey
Do you really think that Australia should host summer Olympics twice during that period while all the aforementioned countries didn’t even host them once combined?
Of course you could argue that some hosted Winter Olympics recently, but I am not sure why you should throw those two things together.