I am willing to bet their life expectancy is double or triple what it is in the wild.....worms, diseases, injuries, rabies and etc. take their toll as well as the known process of when a male can no longer satisfy the females of a pride, he is driven out, or killed, and replaced.
The first thing the new male does is kill any & all cubs around.

For any animal to die, is no greater sin than for any other animal. (Even the human animal , whatever religions may say. ) And in some ways, a good life and a quick painless death such as we hope many farm animals get, (Though I doubt it. ) is better than most creatures, including us, could ever reasonably hope for.

But there are at least three other issues. One, being the waste of material resources, for mere entertainment, the second, is how much needless suffering is inflicted, and the third, whether it really promotes a good appreciation of our fellow animals, to teach people to see them as mere sources of shallow entertainment.

And as the old joke about someone viewing a trophy collection goes. Hunter. "And this is the skin of the biggest and most fierce tiger I had ever seen, which I shot with my bolt action forty caliber. " Viewer. " And what sort of gun was the tiger using.? "