This is because the attempt to change the rules has offered the Senate two options. Both have sufficient legitimacy in the public eye such that whoever controls the Senate can (and does) simply choose the method that gives them more of the long term Senate seats. Unfortunately, this 'dual legitimacy' largely takes the form of public disinterest, uninformed commentary from the media, and to some extent a sense of resignation in the face of the way politicians behave.
Two methods of allocating senate seats The two methods are:
The 'order-elected' method - under this method, the first six senators elected under the official Senate vote counting method get the long term seats. This is analogous to 'first past the post' voting for a multi-member electorate, in the sense that the senators with the largest block of first preference votes get elected first. This is the 'old' method and has been used in every full senate election in Australia's history.
The 'recount' method - under this method, after the 12 senators are chosen, a recount vote is conducted in which only those 12 senators are in the race, and only 6 (long term) senate seats are up for grabs. This is almost equivalent to holding a regular half senate election, except that all but 12 candidates are eliminated in the first round of vote counting (and those votes are distributed according to preference). In practice the outcome will be identical to a regular half senate election. This is the 'new' method, and has never been used.
The new recount method is demonstrably fairer, more representative of the will of the people, and is supported by nearly every politician, including both major parties, except when they have a vested interest in sticking with the old method. The moral gymnastics and backflipping from politicians on this issue is disturbing and disheartening - almost as disheartening as the resignation and disinterest from the public.
A difference of two seats The recount and the order-elected method produce different election outcomes. We have had two double dissolution elections since 1984, when legislation was passed requiring the Australian Electoral Commission (AEC) to conduct the recount so that the Senate has the option of allocating long term seats using that method. In both cases (1987 and 2016), the difference was two long term seats. In both cases, the parties controlling the Senate voted to use the old method instead of the new method because they benefitted by two long term seats, which effectively meant two extra votes on the floor of the Senate from 3 to 6 years after the double dissolution election.
Given the difficulty that the government often has getting legislation through the Senate, two seats is a game changer. It can give one party a majority in the Senate, or it can cut down the number of cross-bench senators whose support must be courted in order to get legislation through. It effectively changes the election outcome, because it changes the legislation that can be passed.
Bipartisan support for the new method Labor was responsible for the initial legislation in 1984 that requires the AEC to conduct the recount vote. In the 1987 double dissolution election, the Liberal party moved to use the new method in the Senate, but was blocked by Labor and the Democrats. The Democrats got two extra long term seats at the expense of the Nationals (and Labor got Democrat support in the Senate).
In 1998 and again in 2010, Labor and the Coalition passed bipartisan Senate resolutions to use the new, fairer method. Unfortunately neither of these resolutions, nor the 1984 legislation, are binding. They cannot be binding, as this would violate the constitutional provisions that leave the decision to the Senate. So in the 2016 double dissolution election, both Labor and the Coalition voted in favour of using the old method, because both parties gained one seat. In NSW, Labor's Deborah O'Neill was handed a long term seat at the expense of the Greens' Lee Rhiannon. In Victoria, the Liberal's Scott Ryan was handed a long term seat at the expense of Derryn Hinch. From 2019 to 2022, Labor and the Coalition will each have an extra vote in the Senate that they do not deserve. As if to highlight their ability to get away with anything, the Liberal party followed this up by putting Scott Ryan in charge of the AEC.
Media and public response Despite the significant consequences for election outcomes, the public remains largely disinterested in this issue. The media largely fails to report on the issue, or leaves out the critical details (such as the two bipartisan senate resolutions) that would make the public more likely to hold their parties to account.
http://www.ozpolitic.com/electoral-reform/broken-promises-stolen-senate-seats.ht...Wikipedia also followed suit in not mentioning key details, and it took some effort by the author to get Wikipedia to acknowledge details of the problem and its history, such as the broken bipartisan senate resolutions.