Right, but even for Peruvians, you show up at the both, make your vote and leave, that's it. No thresholds for registering or other stuff, just you and your ID making a vote, even when outside the country. It again makes the US system seem intentionally designed to make less people vote.
If a bunch of politicians can make voting quasi-impossible for certain groups of people by meddling with their polling stations, then you don't have a functioning democracy.
But I'll give you the benefit of the doubt and assume it's actually easy in Australia. That still doesn't really explain why it's necessary.
For people not on the roll, there is a special secondary method of voting called a declaration vote that allows you e.g. to vote even if you haven't enrolled. But this process wouldn't scale very well - these votes aren't counted for days after as they need to check the details you declared - and is intended as a safety net.
This seems a bit like Chesterton's fence...