One is easily manageable, but consider families or single parents with 2-3 small children and the amount of stuff they need to carry with them, buy when shopping etc. ...
Not everyone can afford to move to expensive suburbs or hire a nanny.
I live on the outskirts of a larger-sized european city with perfect public transport and still prefer my (electric) car, since it's so much faster, cleaner, safer and more comfortable. I'd use it much less if I lived in the city center, but it'd still be a reduction in living standards (carrying shopping bags 500m vs. perhaps 100m total etc.).
You can easily carry quite a lot of shopping bags for 2 or 3 kilometers in a wagon if you need to.
Or if you like, you can use a car occasionally for shopping trips (or even a taxi), and for a workday commute and the great majority of other trips, stick to walking/transit/bikes. Even if people just ditched their cars for 80% of their trips it would make the city overall much more pleasant.
Beyond that, the poor, disabled people, the elderly, and children between the ages of about 5–18 have a much better time living somewhere that they can be independently mobile instead of needing to rely on someone else driving them around.