Nitrogen is used in aircraft tires on USN aircraft carriers. Reason being is it's an inert gas so if there's an aircraft explosion or fire, whether it's from the split rim design failing or something else, the gas won't contribute to making the fire worse. On the other hand, the oxygen in compressed air will force feed the fire making it hotter and more difficult to extinguish.
I don't see any real positives in using it in car tires... hope this helps.