Actually your question should be reversed. :)
People generally ask the reverse question.
Diesel cars are good for those who have long distance commuting on daily basis. Diesel engines give better fuel consumption and deliver better torque. This means diesel engines make everyday driving cheaper and an easy experience. Moreover, diesel cars have run far more miles than the petrol ones before they ask for any maintenance, i.e. running life of diesel engines is much better than petrol engines.
Finally, as a fuel, diesel is cheaper than petrol in India. Even in other countries, we see that the litre price of diesel is significantly cheaper than the petrol’s price.
If you ask why some people still prefer petrol car would be price of car,evethough price of diesel is lesser than petrol,diesel engine cars cost more than their petrol variants.
diesel vs petrol calculator : http://aravindavk.in/diesel-vs-petrol-car/