I think everybody understands that “war for oil” is not necessary to secure the flow of oil to the consumers. The consumers do not benefit from a bloody battle for control over resources. But such a battle may benefit those businesses that end up winning the war for oil.
In a civilized society, of course, there would be no war for oil, anymore than there would be wars for the ingredients used to produce jeans and coffee cakes. Finders keepers first, and buying and selling later. War for oil is an occasion when theft is preferred to honest toil. But in this sense it is again no different from violent conflicts over any other useful resource.