["If the war between the Northern and Southern States was driven by slavery, why did the The Emancipation Proclamation fail to address slavery in the North? If the war was driven by the righteous indignation of the North, why The Gettysburg Address, one of the most important speeches during the war, fail to address slavery?"]

Because slavery was guaranteed by the U.S. Constitution. And the only way the U.S. could officially end slavery was through a constitutional amendment. Which is what the Lincoln Administration managed to jump start by 1864-1865.