Why is it my natural inclination is to root for the underdog?

I think part of the answer is that I've lost so often in my life from sports, to getting the girl, to races, whatever and you name it, I swear it seems like I've cornered the market on losing. That has to be part of it, I think I'm projecting my own inadequacies into anyone or thing that is an underdog and just automatically root for them. I mean it made the Rocky films millions of dollars, having the underdog, no chance fighter come out on top against all the odds. It makes me feel good when that happens, that's why I always root for the underdog. Of course when I'm rooting for my favorite team, I want to win a hundred to nothing, but that is another blog for another day. I guess that'll be my killer instinct blog!