My guess is that the airlines are waiting for something resembling a "signal" from the Australia/New Zealand governments that things will actually open back up. That's probably the difference between, for example, AA and BA even sending a plane down thataway vs just letting Qantas figure it out. Were the government down there to announce that they expected to maintain a hard quarantine in Australia/New Zealand, I wouldn't be too terribly shocked to find the rest of *A/OW would just opt to throw up their hands on the region. Only SkyTeam might have a reason to keep flights in place (and only then because Virgin Australia, which was bound up with Delta, pulled out of the international market).

The bottom line is that until ScoMo decides to clearly signal to airlines that international travel will be able to resume without a two-week quarantine and/or increase capacity to a level that can support more flights, everyone is being a bit cautious. Remember, until fairly recently it was presumed that once Australians got vaccinated the quarantines would be either eliminated or reduced (i.e. some areas exempted). That's now gone out the window and I think it's putting a bit of a damper on airline enthusiasm here.