It can be wise but not essential.
If you're injured while visiting New Zealand, the Accident Compensation Corporation (ACC) may be able to help you. It doesn’t matter if you’re not a resident.
However, you will still need travel insurance for what they do not cover (click here)
Their no-fault scheme covers everyone, including visitors, who are injured in an accident in New Zealand.
You’ll receive the same cover as everyone else if you have an injury while visiting New Zealand.