The math doesn't math when the city grows around car-centric design. All the extra space taken up to separate people from unpleasant high-speed roadways, all the huge parking lots, the extremely-wide roads, it pushes travel times up so much that between the extra distance between everything, and the time spent earning money to pay hundreds a month to have a car (insurance, depreciation, maintenance, gas) ends up significantly exceeding the benefits of car ownership.

They're wildly nice if only a few people have them. The more do, and the more parts of a city cater to cars, the worse they get, even as they also become totally necessary (so, not having them also gets far, far worse, even untenable).

I was introduced to this notion reading an analysis from some French social-philosopher and was initially like "that... can't be right, surely?" so ran conservative numbers on my own situation, with an average-or-better commute distance for my city, a cheap paid-off car, and nearly double median individual income for my city, and... yep, dude was right, living in a city designed around cars was costing me time, not saving it. It'd be a ton worse for people with worse commutes and lower-earning jobs. They were getting totally screwed on the deal.