Are you sure of that? The only people I know who are doing an MA here in Australia are those who want to do a PhD in the UK, because they can't get admitted off the back of an Honours degree. (I only mean those who actually want to stay in academia; I'm not counting people doing MAs here for professional reasons.) And my mate from New Zealand was a little pissed off that he did an MA there because if he'd known he could've come straight here from Honours he would've - but then I remind him he didn't choose his topic until late in his MA, and he only came to Australia because his preferred supervisor was here. He could've easily chosen a topic/supervisor that would've taken him elsewhere, and wasn't to know the Australian system doesn't require an MA for admission to PhD. I was also talking to someone from France last week who was stunned that it's not normal to do MAs here first, and my colleague from Germany indicated the Australian system is not normal in this regard either. It certainly stands out on the CVs of people in our department - those who studied only in Australia don't have MAs unless they're really old, while those who came here from elsewhere or went overseas for PhD also have an MA to their name.
The American system is very difficult to compare, since your PhDs take fucking a billion years. Our PhDs run for three years (though most scholarships allow for one six-month extension, which everybody takes because free money).