We must know different people in NZ and Australia, because I disagree with the inference their citizens treat politics like the weather report. One of the biggest differences at least in NZ is that there exists MMP for voting, which allows NZ to avoid brinkmanship in policy and winner-takes-all mindsets that lead to sharp divides.
It's not quite that it's unimportant to people I guess, it comes up in conversation during election periods of course. People just aren't particularly partisan or passionate in my experience. I think most people have other things they would rather talk about.
Similarly as the comment above mentions, Australia has preferential voting which helps in reducing the overall divisivness of the two party system most democracies end up with.
