The regions have always had to support NZ as it has been the only way to get anywhere.
Other carriers have stepped into fill voids in the past but as soon as they start to make progress Air NZ has squeezed them out, they will then continue to offer a service until they decide its not profitable then the cycle will start again someone new steps up in a year or two NZ will decide they want it back.
The people who jump on the likes of EK/SQ/CX are from the main centers who don't have to take an NZ flight to connect the regions dont have that option.