Honda showed an appreciation to its customer and another advertisement campaign for them that they are showing this to world that how reliable their cars are. At the end of the day, giving away one car to its customer won’t harm them every any possible way but would bring more customers to Honda.
By the way, 1 million is equal to 10 Lac so majority of people in Pakistan have surpassed this milestones number of times as all the cars which have been bought since creation of Pakistan has never been sent to scrap yard and they are still running on roads. Since we are a third world country that’s why car manufacturers never bother.