Thank the gods we live in such a car-saturated nation, how horrible it would be if this space was used to house people

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.