Imagine how much more you could do if material needs were fully taken care of without effort. If you didn't have to work a job to put food on the table, a roof over your head, and clothes on your back. All of that is out of the equation. You could devote yourself to any endeavor, be it self-improvement or pursuing something for the betterment of all mankind. Or both.
EDIT: I don't think AI will send humanity to extinction. I think we'll do it ourselves. Someday, some human's going to push a button and that will be the beginning of the end. I have no illusions any more that the hopes of my childhood that I would grow up and be living in the Star Trek Original Series will come to pass.