Sure there are those who cannot afford a car, but that isn't what the article is about.
Not necessarily so.
I live 2 minutes from two tram lines and two bus lines.
I live 4 minutes from a train station with a train every 15 minutes.
It takes my 12 minutes door to door to the central train station and 25 minutes door to door to a 2nd tier European airport with excellent world wide connections.
I'm a member of a car sharing cooperative with about a dozen cars within 10 minutes walking distance. I don't think that I rented one in the last two years because I just didn't need a car.
And all this has really nothing to do with my financial situation. It's just that owning a car with public transport connections within walking distance would not add to my mobility in any reasonable sense.
Personally, I am walking 40 minutes each way to go to work, or uber in the morning and walking in the afternoon. It's not that I can't afford a car. I am just not interested in owning one.
Also, I'm pretty sure that many "anti car" teens still know someone, like their parents or a friend, that owns a car and can help them out occasionally.