Some carnivores do, but it is true that most don’t seem to. If a carnivore goes after another carnivore, it would probably get more of a fight for it’s meal, since the other carnivore is designed to hunt animals too, not just plants. It’s probably just a matter of what’s easier. Great White sharks generally kill with two hits to reduce chance of being injured or losing extra teeth. On the other hand, Tiger sharks just don’t care, and will happily eat other sharks. Some Orcas have actually taken to eating Great Whites! They’ve figured out that when you tip a Great White upside-down, it essentially becomes paralyzed, making it an easy meal.