I don't understand why a backup service would need to setup regional infrastructure. It's not sensitive to latency, the bandwidth costs the same and it adds management overhead.
Not sure about Australia, but the most common reason would be local regulations (i.e. laws forbidding to store certain data outside of the borders of a particular region). But given we're talking about Australia, I would not rule out the latency at all.
In Australia it might be to attract Gov clients? Not sure why the Home service would matter though other than Australians are big on using services located in Australia.