Great question. Even though I could philosophy a lot on this certain topic, the answer is somewhat simpler. 

What I believe is the main cause, despite the probable wrong ways of raising children (it goes way back in the family tree - as our ancestors were raised wrongfully as well), is the programming we are undergoing for centuries, if not longer.

The program so good that it made us to forgot what we truly are. You see, I am you and you are me. Below these skins, and everything you think defines "who we are", we are identically the same. We are all one - connected, just like the picture on my avatar. 

That is why, from the ancient ages, people in power or the Elites (call them however you want) did all they could (in their power) to divide us on as many levels as you can imagine. 

Today, we are divided not only by race, nationality, genders etc but so much more. Just think about it, people divide themselves based on the club they are cheering for (illusion), so yeah. I think this one is pretty self-explanatory

Until everyone realize how we are all one, identical (divine energy expressed in the Universe that gained consciousness through the brain), the BS will continue & the people/entities in the shadows (you aren't even aware of) will continue to grab everything on their path & use us as a RESOURCE!