The laws changed around semi automatic centerfires after a shooting "massacre" that happened over 20 years ago and the laws have never changed since.
New Zealand doesn't have shooting ranges like you do in the US where one can pay a fee and shoot at the range, and our hunting laws are different than yours also, as well as the public land you are allowed to shoot on.
The assumption is if you want to compete with a military style rifle or want one for hunting/fun then you will go the route of getting the correct licence and then buying those types of rifles.
I live out in the country and about a month ago a man turned up at a neighbors place asking where down our road he was allowed to shoot, as he had just got his licence and a gun. Now no where down our road is there anywhere that anyone can set up some targets and shoot, as it is very steep and very thick bush so you couldn't be sure you were safe to shoot or not..
It is also only a small block of public land and it is completely surrounded by farm land and houses and a few roads. And it's not even very good hunting anyway. So I'd rather not have people who don't know what they are doing, on public land that don't know the area or the lay of the land being able to fire off hundreds of rounds at there will.
I do know exactly what you are getting at, and I think you do have a point for in the US, but we don't have the same shooting culture or the same facilities for people to shoot here.
The system is set up quite well and we don't have anti gun people trying to get at it constantly, so it does work the way it was meant for. As it's not overly difficult to get the type of licence you need if you are a genuine person.
That being said there is still gun crime here, but not very much, and it's very very rarely with the type of these guns that are restricted but have been obtained illegally, or by someone who obtained them legally.