I kind of agree with Lead Sled / Jack Ranga, but think the stumbling block to WAAS is that the airlines don't need it. The hockey stick high traffic routes are served by ILS and no where else really matters.
Although (with less sarcasm) most other locations in Australia have good enough weather than GNSS NPA is good enough.
It should be noted that Australia does have WAAS beacons, but they point to sea for marine use and are not usable for aviation.