Because Earth resources are limited. Because most of humans are greedy and jealous. Hatred, intolerance rule the world. (You may argue with the last thesis, but it is an obvious fact - even if not everywhere.)

How misanthropic I am.

lanfren is spot on. Greed and jealousy are two of  the prime reasons of war. Add to that pride & arrogance.

And then rest of the bad stuff like hatred, intolerance, etc. will follow automatically!

Because it's easy to fool people into blind obedience. Because it's easier for people to follow orders than to think for themselves.

War happens because of conflict in every individuals interrest. I believe that it will end if we change our attitude by becoming humble and forgiving. To create an open communication with one another and to respect every individuals autonomy. And the change we wanted to see in the World should start within us. :)

for money , new lands     , have power and be famous....