Why Countries must go on War?

Why Countries must go on War?
With the current bad economy situation, everyone had been suffering to stay alive and try to find way for living. Government should look on ways or implementing certain programs or plans to help those people to survive in the current situation.

However there are countries that over-look on this and only invest the government/people money for "War", "Weaponry" and "Terrorism". Is all this is necessary when their people need the help the most? Why must go into war? Currently there is war in the Gaza Strip along Israel and Hamas (Palestinian Sunni Paramilitary). Innocent people are being killed because of the war (air strike and now ground war). What kind of benefits the countries can get for this war?

Nowadays, the information can be traveled across to Atlantic or Pacific Ocean much faster than the older days. Any action you make, whole world will know about it within the same day. Eventually it had caused problems at other countries with street demonstration protesting the war. This had caused unrest among the people at the affected and unaffected countries when the economy is sliding downward. Where is the consideration attitude among those countries?

In this world, everyone has his or her own differences or own problems to solved. Why can't we just learn to be tolerant with each other and accept other people thinking or action without triggering a "war"? We got different culture, race, language and many others. We must learn to accept each other and not acting against each other. If people really don't want to tolerant, people around the world shouldn't travel across other country, everyone should stay and do business in own country and never leave the country. Then nobody got any differences and just live in the world of their own.