Who said anything about enjoying killing animals? Sense of achievement of a job well done. Less ferals killing the native fauna and flora. Or meat in the freezer. Or less pack dogs killing sheep.
Plenty of opportunity to teach youngsters how to do something in a responsible fashion. Just because you can't doesn't mean others mustn't be allowed to.
As for my last sentence, well, you brought up the beer at 18 analogy. But they can legally get pregnant at 16.