Why are people so hung up on fairness?

I can’t recall how often I have heard that we humans are just animals of higher function. Let us run with that a bit. In the animal kingdom it only works because there are predators and prey, those who do the so-called victimizing, and those who are just victims, if they are not smart enough not to be. What is fair about that? Some are born lions, others are springbok, wildebeest, etc. which are food for the lions. The game is not to end up on the menu of those higher on the food chain. In life there are those who prey on the weak, or those with less power, being mere animals of higher ability then it would be up to those in that category to avoid, hide, or outsmart those who would victimize them. If they can’t, don’t or won’t natural selection take its bow, and they are victims. Why are people so hung up on fairness? The animal kingdom doesn’t have fairness just a pecking order.