What has tended to happen is that there's coalition between the Liberal and National parties. In places where they have been strong, they wanted to bring in compulsory preferences to maximize that preference exchange. For example, there was an incident in the spring in Queensland where there was debate over reapportionment of the legislative seats, and then the Labor Party brought in an amendment to bring in compulsory preferences, because they had been bleeding votes to the Green Party and others and wanted to make sure they'd recapture those votes. Parties that think they're losing try to maximize that.
Australia also has really complicated deals, because the senate uses STV, where the larger parties will make a deal with the small parties to make sure that on their how-to-vote cards, they put them as second choice, and in exchange they'll tell their supporters to indicate the small parties on the senate ballot. There's a very complicated system of deal-making that goes on between the two houses. The compulsory preferences are a very big part of what makes that work.