The world is just structured in a stupid way. Why does an eagle have to kill a rabbit to eat? Why does one creature have to die for another to survive? It's an idiotic world, honestly. I can't imagine what kind of idiot would come up with such a system.

Why? Probably because it's natural. This "world" arose as a result of a series of coincidences. That's just how it happened. And when there's competition and a struggle for survival among animals, it creates an incentive for them to evolve.

The beauty of it is that, unlike that eagle, you're a human and you have the freedom of choice. You don't have to kill. In theory, everything is great, but I'm almost certain that you, like anyone else, cut up earthworms when you were younger, regularly killed mosquitoes that dared to land on you, and squashed cockroaches that wandered into your apartment to collect crumbs from the floor. And everyone wants to eat, you know.