I don't see why people need another car. Its going to lead to more traffic jams, congestion, pollution and a waste of petrol and diesel. People can instead walk, cycle to places or make use of alternative transports like taxis and buses. It will help them stay fit, save fuel, reduce pollution and congestion.
A large family may need more than one car to cater for everyone and to travel elsewhere.
If someone has a particular job that requires them to drive a car that they don't like, they should be able to buy another one that they do like.
Also, if someone can afford several cars, then I believe they should be allowed to. I don't see how anyone could suffer from that.
Of course, if they want to be green machines, they can not have a ride to work. But i believe that we are going to hit another pocket of oil and all of those who decided to get rid of 1 or 2 cars will now be screwed because now gas doesn't cost as much and they only have 1 car.
One car per household would mean everyone would have to fit themselves into each others schedules making it impossible for a larger family or families to A.( get to work B.( have transportation to and from school C.( have transportation to activities. The matter of an emergency also rises. For example if the car is being used by one person in and something happens to one of the other people at home where they would need to use the ER their amount of time to get there would increase substantially compared to the amount of time that it would take them if they had their own car.
Also with one car what happens if it breaks down? Has a flat? Wife needs to start work at same time school starts for the kids? I currently have 4 cars to my household which I'm blessed and glad. First reason my new work truck has been in the shop for a faulty rearend 3 times in last 2 weeks. My wife's new used car is having a starting problem and we have only had this car for 2 weeks. Her previous car is a classic custom painted reliable daily driver that will get her to work if the car won't start. My 4rth cat is a old elcamino that I'm restoring with my kids to teach them good mechanical skills. Most kids these days don't even know how to check the oil... So yes I think more than one car is the way to go if you can afford it..