According to Wikipedia the Nationalist Party of Australia introduced Preferential voting to prevent vote splitting when two conservative parties were running against a single leftist party.

It is amusing then to hear modern day conservative voters complaining bitterly about the preferential voting system, arguing that in many seats the local Coalition member received more first preference votes, but due to preferences flowing from The Greens to the ALP, they lost the seat.

Despite bringing in a system specifically to avoid the requirement, they still persist with "The Coalition". Of course, without it, the ALP would easily have more of these precious first preference votes. On the current count the ALP has 27 seats more than any other party.