Whenever I fly SQ into SIN from Australia, there are so many QF Gold and Plat pax on the flight, just by observing hand luggage and checked luggage tags.
If QF only offers 1 flight a day from MEL and SQ offers 4, which would you choose? Further, if you ran a business ex MEL, would you want your staff to waste the entire day getting from MEL to SIN on QF, or would you like him to have the choice to leave on the 1900 arriving SIN at midnight, allowing for a full day of work the next day and the day of flight - or if in J, you could even put your staff on the overnight from MEL departing at midnight arriving at 5.30am?
If you run a business ex SIN, would you like your staff to waste an extra night of accomodation in MEL just to take the 10am flight back, or would you put them on SQ so that they can come back at 7pm or on the overnight? Of course ex MEL there is also EK which leaves at 7pm - but that's not a QF operated flight is it, and even if booked on the codeshare I wonder how much benefit QF gets out of it