I don't know of any country that has a social safety net that 100% reimburses you for a life-altering injury where you can no longer work. Sure you'll get a disability pension, public healthcare and maybe a bit more, but it's usually "barely enough to live on" support.
If you're a doctor making $200,000 per year and you can't work again, suing is usually the only way to recoup things like lost-wages.
In NZ people can still sue over business contracts and participate in legal cases against the government culminating in legislation being ruled unconstitutional, like other Anglo, common-law countries.
It is rather bug difference.
Also, insurance companies when they settle claims, they force you to formally sue the other person or they sue each other. Most of these are routine formalities. Again, system setup in a way to generate suits.
All kinds of other tort suits exist, it's just that people without any money don't know it, they have no lawyer and nothing to sue or be sued for. So we go around saying "we don't have a culture of suing, that's so American".
In actual fact, wealthy people here are just as litigious as anywhere else... as you are when you have something to gain or to lose.