✔ 最佳答案
The right answer for this question probably deserves the Nobel price for peace. If only someone figured it out, then something could be done about it.
My best guess, lack of education. People who learn to think for themselves and be skeptical, know that fighting doesn't make a problem go away, it just causes misery and destruction.
Update: The only exception to this rule is the United States. With the wrong politicians, they still go to war for financial gain for a few, and lie to the rest of the world about it.