In my view, there is no need to purchase a car in the big city, if the city has a good transportation system and better connectivity from one place to another. If we do not buy a car we will help our country, our city and ourselves. The most important way is by decreasing air and noise pollution. If we do not have a car we will decrease the rate of car accidents and traffic jam also. In some countries roads are very narrow and if everybody drives a car, it will block the roads. In big city, we have local trains and bus connectivity we should use them and avoid purchasing a car. Use of public transportation will get free ourselves from a lot of tensions. To drive a car we would need to keep a license. Some emergency cash will also be needed while driving.
But many times car is useful also in big cities. Suppose, some body get injured or sometimes you want to go for picnic at that time car is very useful.
Car is not a need of big city if you would like to find a pollution free country or city.