(I do not live in New Zealand).
Take your own risks in life. Don't drive a car you can't afford to replace.
In the "no mandatory insurance" scenario, you're taking the risk that someone else may damage your car. So don't buy a car you can't afford to replace.
FWIW I didn't downvote you. Your post is borne of ignorance of how it works in the US, which is actually enviable because it means your healthcare system isn't an absolute wreck :-)