When was the last time that congress voted to officially declare war? WWII. I had to check to make sure we didn't declare war for the korean war, and we didn't. Lots and lots of congressional authorizations, but it's a way for congress to cover its bellybutton so that when %#*! goes wrong they can blame someone else.
What can I say, it's written in the constitution that congress has the power to declare war. This goes along with our signing up for all sorts of treaties that we break time and time again. We ought not to sign them unless we plan to honor them. Intentionally bombing civilians is a great example of this.