In Norway, the tax authority will send you a summary telling you what you owe or what they owe, and if you don't have corrections you don't need to do anything.
(all bank accounts in Norway are keyed to a national ID number assigned at birth, and the banks report all interest income and loss (as interest on debt can be subtracted from your taxable income), and your employer(s) reports your income)
There are some exceptions, in cases where you have particularly complex tax matters, but most people don't have to do anything any more.
I'm not sure why they don't do that in New Zealand, the numbers are all provided, you just have to type them in.
Perhaps it's a privacy thing?
One of the advantages is that you can check if you're owing money before filing a Personal Tax Summary (they have a tool to check if you'd owe money or be paid money), and you don't have to file for one if you owe money, and as long as it's less than a certain amount ($500?) then they don't care.
My guess is it's just a matter of slowly changing policy. In Norway it went paper return => online return => online summary that you had to confirm => summary that you only needed to act on if you had corrections. That process took many years, I'm assuming as they wanted to iron out any issues with one step before taking the next.
(all bank accounts in Norway are keyed to a national ID number assigned at birth, and the banks report all interest income and loss (as interest on debt can be subtracted from your taxable income), and your employer(s) reports your income)
There are some exceptions, in cases where you have particularly complex tax matters, but most people don't have to do anything any more.