Bloggsy, a quick duck into Noumea or Brissie for a top up isn’t as easy or practical as it sounds.
By the time we land in either we are adding at least 90 minutes to the flight, getting a gas and go done on an unscheduled basis isn’t all that quick, and add that 90 or so minutes onto a duty period already sitting around 15-16 hrs and it is all turning to crap rapidly. LAX-SYD is already around the 15 hr block time mark, plus sign on and you can see it is a long day getting longer. LAX-MEL is much closer to 16.
getting flight plans, load sheets, fuel and a gate to park at on short notice isn’t all that easy a prospect and I reckon turning around in 90 mins is pretty good going.
there isn’t anything special about transpacific flying other than the fact that you tend to leave the US at max weight, so you can’t bung on too much more fuel, LA as an example has a thing about taking off into wind at night which further complicates things, and these issues make it a bit of a planning challenge, so throwing on a lot of extra gas for Mum and the kids isn’t all that practical in some cases (not always but a lot of the time) so while it isn’t a big drama to throw on 30 minutes of fuel in a 737, 320 or 717, putting on an extra 6-8 tonnes in order to have 30 or so mins available at the end of the flight is severely restrictive.