Online Flight Booking | Airfare | United States - Cathay Pacific still shows flights available daily throughout October 2016 as available to purchase a ticket.
CX157 schedule. (Cathay Pacific flight: Hong Kong -> Brisbane) shows you the slight variations in departure times and the dates that these schedule changes occur.
Hard to say why your flight is cancelled without further information from you.
The fact you are using 2 different airlines may hold answers as there could be many reasons to speculate on, including connection times insufficient due to seasonal schedule adjustments.
But guaranteed: Your stated cancellation of the flight(s) is not because CX Pilots choose to not work on days off.