when I think of NY drivers I picture just cab drivers...and no one actually owning a car
When I was in Italy a few years ago I heard that they actually have fewer crashes - not death rates but just crashes - per capita than in the US. If you think NY cab drivers are scary, you have seen nothing until you've been to Italy and its 8 ft. wide roads and CRAZY-ASS TERRIFYING drivers. But they hardly ever crash.
I think that is explained just like the OP is: you have to always be alert in condensed areas when driving - especially condensed areas that are known for erratic drivers - NY and Mass. have been mentioned, and I grew up right outside DC and believe me that's tough as hell too. People are just better, more conditioned drivers in those areas.
I also think driving a manual as opposed to an automatic keeps you more alert. I would be willing to bet that manual drivers have a disproportionately low accident rate, despite that fast, risky cars purchased by aggressive drivers are more likely to be manual. Just a hunch.