Taupo is a busy and ever more popular tourist destination. It already surpasses Rotovegas for movements and that is because it is a much nicer destination with a clean lake and many more activities. The runway will get lengthened one day to meet the demands of tourism, the aircraft servicing Taupo will get bigger and, it is inevitable that it is going to need control one day so why not implement it while there isnt a huge amount of traffic so that all the irregularities can be ironed out. I think the operators there are just worried about the extra costs but it is only the extra cost of controllers because the infrastucture and procedures are already in place!
Having flown out of there many times, I think Taupo would definately benefit from ATC but unfortunately it is a bit of NIMBYism creeping in from the Taupo based operators.