Why should we commemorate World War 2?

A lot of people died during the World War I (though admittedly not as many as World War II), there are many technologies that were implemented or improved because of World War II, there was a huge amount of racial and religious genocide in German occupied countries, a number of countries were taken over by the Nazis, the problems of the Cold War date back to the Second World War, the great time of esponiage was during the Second World War, and there are two nuclear attacks on Japan and its huge human and environmental cost. Not to mention the need to study sociopaths like Hitler and how he had such a huge effect.