The reason to want to live longer? One word: space.
Living hundreds of years in good health will allow us all to become a space faring race. It will allow us to take the long view on interstellar travel, our species and relationships. I'm hoping to see that day and having Steve leave so early only solidifies the importance of longevity in my mind. Intelligence is not meant to die, it's meant to live. We accept death only because we have to and have been powerless to stop it. Technology is starting to change all that.