There are wild places in Oz. You cock up your nav and get lost, it could be decades before anyone finds the body - go look at the museum in the Alice.
There are wild places rather closer to Brissie than to Perth I think? - certainly a bit further north, round Tully say, you've only got to fly half an hour inland to get to country you really wouldn't want to get lost over.
It could also depend on what you asked for - you don't need the outback nav briefing and test if you're not leaving the farmland round Perth, but you might be well advised to take it if you're wanting to do XC from Brissie other than up and down the coastal strip?