Originally Posted by Thai-Kiwi

NZ and some other countries can use SmartGate, others have a face-to-face immigration experience with an Immigration official. We all potentially get the same customs treatment.

The purpose is to determine whether or not to grant entry to NZ and under what conditions. Whilst almost all pax are legit, flags are raised on a few - including those holding a visa.

[slightly OT]
Having a Visa doesn’t guarantee entry, it is effectively just a (initial) screening which gives confidence (but not absolute sureity) to the airline that the pax is OK to board at origin, and to the Customs official on arrival that the pax has been though a process and has made certain declarations on the purpose of their travel. But they can still decide not to issue an Entry Permit ( the old inky stamp or now electronic record). The differences between a Visa and Entry Permit are not well known - since almost all pax don’t have .a problem.

And of course some countries just use the visa as a revenue source and/or reciprocity for what NZ requires of their citizens who want to travel here
[/slightly OT]