Why Indian people throw trash out train window?

Recently after very long time I travelled in sleeper class train and saw that people simply throw trash like empty plastic bottles, plastic wrappings and paper out the window. And both sides of the train track is filled with litter. Same thing at almost all tourist spots and cities in India. This massively decreases quality of life of people in India and prevents tourists from visiting India. How can indian government raise awareness about not throwing trash anywhere but instead carrying it back home?