Why do people care about sports?

I don't want to be mean or patronizing, but I honestly don't get it. I understand why people play sports, I understand why people like watching sports, I understand why people follow sports teams, I just don't get why people actually let the outcomes of games effect their mood, especially when it makes them sad or mad. I mean, what's the big deal? I understand if you are betting, but otherwise, why does it matter who wins or loses?