I apologize if you're being sarcastic, but this is the point. We need cars because we designed our cities around cars.
If we designed around foot traffic and rail, we wouldn't need (as many) cars and could do with less expensive car-centric infrastructure. Not just interstate exchanges, but also the massive parking lots and garages that are required, gas stations and car repair/oil change places on every corner, etc.
An apartment in the suburbs of Nowhere, Texas? Agreed. An apartment in the middle of a beautiful, historic downtown city center that has been developing for hundreds of years? I could give the car up.
That's not going to solve it for me, unfortunately. I really value privacy, personal space, and quiet. If I were surrounded on all sides by other families I assume I would leap from the window in like 10 seconds.