Honestly my bigger confusion are the fairly large swaths of NYC well served by the subway that still have more people using a car - most notably the area around Midwood in Brooklyn and Gun Hill in the Bronx area.
Midwood, I would wager, is just a quirk of choropleth mapping, as I think there is probably a significant walking contingent like nearby Borough Park composed of many Chassidic Jews, enough so that the transit percentage drops below that of auto users.
The area you call “Gun Hill” - Pelham Gardens, Williamsbridge, the like - is actually kind of interesting. There’s a little profile of the area in
the Times that encapsulates the “vibe” of the neighborhood better than I’d be able to describe, but it really is more of a “suburban enclave” (emphasis on
enclave) than you’d expect of an area in that part of the Bronx.