Sooner or later, many people work out that there is no substantial difference between Labor in power and the Coalition in power.
When the electorate is programmed to elect one or the other, both of them win. They know that their turn to suck the body politic dry will come around eventually. That's why, for example, the frequent travel and allowances scandals always involve politicians from both 'sides', but rarely lead to any substantial changes. It's also why the same people have been running aviation regulation in Australia for nearly two decades.
Whether people come to this realisation before they're thrown on the scrapheap is a different question. Given that it's still generally a one-side-or-the-other debate in Australia, I guess that many voters are still slow learners.