Large parts of NYC (much of the outer boroughs) are not near the subway, and not within walking distance of a supermarket (especially if you're carrying groceries for an entire family). Millions of people live there because they can't afford Manhattan rents, especially for a family-sized apartment.

Also, transit lines tend to connect well to mid-Manhattan but poorly between other locations. So if you live in Queens and work in Brooklyn, good luck getting to work reliably by public transportation. (Before you object to that arrangement, consider: If you own a house and have kids in school, you're not necessarily going to uproot your family and move just because your new job is further from home.)

Thus, many ordinary New Yorkers rely on cars to commute to work.

Some parts of Brooklyn are much nicer than the ratnest known as Manhattan. Manhattan is so overcrowded. It's a bad place to raise a family. Someone can literally shoot or stab you in broad daylight and easily get away with it. All they have to do is merge into the crowds of pedestrians. Then perhaps they descend into one of the many subway lines, conveniently escaping, scot-free.

when first living in NYC I had a station wagon, previously gifted to me. Not being from the area I couldn't believe there wasn't a decent supermarket. I had another friend out in Long Island near one. I got several Manhattanite friends to come along, none having ever driven. The experience was hilarious, all around. From the traffic, the experience of a wallowing beast of a Pontiac wagon on the LIE, and then the best part, one guy who'd literally NEVER left the City absolutely MARVELED at the selections as the store. Notable quotes being "I've only seen this brand on TV!" and "How could anyone EVER need a TWO-GALLON SIZE tub of laundry detergent?"

I did a quick google map survey and found that it can take about an hour to commute on public transit between a residential area in Queens and to a commercial area in Brooklyn[1]. Not ideal until you see that driving the same route takes about 40 min. So not a huge different and definitely passes as an alternative to avoid the risk of stop-and-go traffic jams.

If you need to drive to the supermarket you should have the option of choosing a time and route with minimal risk of traffic jams. I find it hard to belief that many people are frequently hitting bumper to bumper traffics on their way to or from the supermarket. Occupationally yes, but frequently no.

1: https://www.google.com/maps/dir/84-25+168th+Pl,+Jamaica,+NY+...

82.2% of Staten Island own at least one vehicle. Averages aren't the greatest summary statistics..

The population of the tristate is nearly 20 million. Even a tenth of that is a lot of cars on the road.