For your own benefit mostly. If you want to spend some time for the benefit of society at large, so much the better. But at least you should care about your own benefit.
Your replies seem to indicate that he should spend his time doing "productive" things instead; that would be more "optimal". I guess I'm tired of this race-to-the-bottom mentality where we spend so much time "optimizing" our productivity that we optimize the joy out of life. Productivity is a good thing, but I'm not convinced it is the greatest good.
