We live in different worlds even though we are habitated on single planet -- earth. In school days it took years for me to understand caste system at our town since we lived in priviledged campus of college area. Apart from college activities there was not many other activities involved so couldn't able to know that people are borned in particular work related families.
College, job where you start understanding depth of caste system since you get to know how many seats are "reserverd" for YOU. Depending on what category you are you start blaming your failure at admission based on your caste. Whatever admission you get in, you look forward since you have college and think that this can only happen in India.
This perception also changes when you step out of India, you start watching discrimination based on race, nationality, religion, gender. Even so called developed countries are not behind it, if not rest of discrimination but based on financial status -- social classes do exist. So we can safely assume that we live in classified world.
Once we are aware of this classified world, our approach throughout our life is fight for our own "class" be it our belief, way of thinking, cooking, talking. We try to admently stick it to preserve our class. Once this happen within family also class war begins... for trivial matters. It is very important to understand person - "class"wise before interacting with him.