...snip...
because australians abbreviate almost everything, unless the name has only one syllable, in which case we will add one and lengthen it, i.e. uluru or ayres rock is known as the rock, john will be called johnno
also because australians tend to blur the sounds in their words, so australia is pronounced oztraya
the wizard of oz may also have been influential
my theory is that this happens because it gets so bloody hot here that we can't be bothered with the effort to talk properly......
.