Nadi and Houston are one or two offs for the day so makes sense to hold. Akl to Syd happen all the time so they will just put you on the next flight. Also guessing you may have been only person going via Akl to get to Sydney on that flight (would guess the vast majority of people in Chc would fly non stop from Chc to Syd?), so no point holding for one person, guessing the other had more transfers? Next flight to Syd was less than two hours.

When you had other airlines put you on other airlines what was the wait if went on their metal? Suspect if you were in LAX and wanting to go to LHR or vice versa they might be more likely to use another airline as only once a day and the if the loadings are good might not be room.