Couple of things, the border has only opened very recently and the rules in each state still haven't harmonized yet. Second, the airfare of these short hops across the Pacific aren't particularly attractive. $1,600 to fly out to LAX seems a bit pricey to me (I suspect they'd have more takers if the fare was about half). Third the airlines haven't communicated to the general public what travel is like in this new environment. Today sort of reminds me of October 1, 2001. Yes you could technically fly but there were a number of things up in the air when it came to security and other things. It was only once those things got normalized and the airlines communicated that new reality that travel began to pick up (I reckon that was around 2003 although those with more knowledge please correct me).Tonight's QF11 from SYD to LAX, A388 VH-OQB, only had about 125 booked in whY, so heaps of empty seats.
I gather this is common for many international flights in and out of Oz at the moment. So many are deciding not to fly overseas this calendar year, and seemingly not even domestically (though time horizon may be shorter).