I get why this was the very last thing Phil Schiller mentioned during his long unveil of the iPhone 7 and iPhone 7 Plus. But for some people, it might be the most important. The iPhone 7 has a stated battery life that's two hours longer than that of the iPhone 6s, and the 7 Plus offers an hour more than the 6s Plus.
In the case of the iPhone 7, at least, that might be difference between your phone dying on you and getting through the day on a charge. HM