Why so much war?

I am concerned about all the war (and threats of war) in the world today.

U.S. troops are stuck policing a civil war in Iraq.

U.S. troops are still in Afghanistan after more than four years, with inadequate support and a resurgence of the Taliban.

Israel and Lebanon are pounding each other with bombs and missiles.

North Korea is waving its nukes in defiance of U.N. sanctions.

And, as many Americans are still unaware, there is genocide going on in Sudan.

Why so much war?

Why so much hate?

Why so much aggression?

Why so much indifference?