I suspect that the expanse of the density around NYC is also a contributor to why people are less inclined to own cars there. As you say, 30 minutes from Boston can put you in, well, perhaps not farmland as such but certainly woodland areas and generally uncrowded areas of seashore. 45 minutes to an hour will put you in apple orchards and genuine farms.

And you can't get to most of those places easily using public transportation. Which makes not having a car you can hop into quickly more of a sacrifice than in NYC where driving out to "the country" is generally a bigger expedition.