Here is a slightly different slant on things. In NZ it is a rule (part 91) not an AIP requirement and basically it states that you always have to carry an alternate unless the weather is above certain specification, where you can (if you wish) depart without an alternate.
Aussie, it is an AIP requirement and it assumes that you always go without an alternate unless the weather goes below a certain spec.
Both achieve essentially the same result but have been derived from different mentality. However in NZ it is a rule and that has teeth above an information pubication.
In Aussie you say "I have to carry an alternate today" and in NZ you would say "today I can go without an alternate".