Easy to guess
Google also test their delivery drones in Oz, because that's about the only place where you can do it legally.
Amazon.com has advertised for a Brisbane, Australia-based software developer to work on a “new and confidential Amazon Fresh initiative”. AmazonFresh is shopzilla's grocery delivery service and has hitherto been confined to Seattle and parts of California. But the company has previously signalled it is keen to bring …
Why doesn't it make logistical (or logical) sense? Chances are that they'll only be serving the heavily populated metropolitan areas. And potentially Oz is a nice learning market before moving into other developed non-US markets, given that there's little similarity between North American markets and many other Anglophone or even European markets.
It doesn't make sense because Brisbane isn't a heavily populated metropolitan area by any global standard - it's a poxy 2 million people that's a day's truck drive away from the next market of any significance, which is Sydney. In addition to being small, Brisbane also has high wages and high shipping costs - three things that are anathema to Amazon's model.