Traffic jams and cost. You can’t be this stupid, can you? I literally pointed out buses take up less space and use less energy. Why ask your question as if I hadn’t pointed out the negatives of your solution compared to buses (or other public transit vehicles).

Also, it’s not quiter or cleaner, since more cars = more noise compared to one bus (you can’t consider the vehicle without considering it’s capacity), and you generate a lot more pollution (rubber tires produce a lot of particles, and you have more vehicles and more tires). So stop lying.

The reason people in cities with proper transportation don’t worry that much about getting a bus directly to their destination is that the network is comprehensive enough to cover all manner of trips, from any one point in the city to another.