Darth Vader is back. Why do we still care?

They saved the best for last in the first official trailer for Rogue One: A Star Wars Story, released Thursday night. A blink-and-you'll-miss-it image of a reflective black helmet, seen from the back. And of course, the gas-mask sound of breathing. 
One inhale was all it took.
Darth Vader, the most iconic cinematic villain of the 20th century, was on screen in a live action movie again — for only the second time in the 21st. Despite the very strong possibility that his screen time in