By your same logic, which I actually subscribe to, why should I give a shit about anyone else? We're all insignificant, myself included. However, I experience my emotions, my pleasures and my pains. I don't experience yours. Ergo, my existence is slightly more significant to me. Which is why I butt you out of the way so I can check out five minutes faster and get on with my life. You are, after all, less than nothing.