This has always been a bit of a cultural stumbling block, it never ceases to amaze me. I'll try to keep this short and simple, in hopes that the caller sees this.

Since the Neolithic Revolution, our species has largely been a detriment to ecosystems around the world. In the last two centuries, this is especially so. Cities, highways, rail systems, everything humans have built within the natural environment that is comprised of synthesized materials not found naturally occurring in nature. These structures have atomized ecosystems and effectively disrupted most of the habitat/range of native species. In this way, we've taken on a sort of "meta-domestication" in most continents; wild animals are a few degrees less wild in the sense that they are continually in contact with human beings (either humans themselves, or the things they've built). Therefore, as paradoxical as it may sound, it became necessary for humans to enter into a "conservation model" of managing the ecosystems. If these programs did not exist, there would essentially be no wild animals. Plain and simple.

In comes trophy hunting. This mainly takes place in Africa, but exists in varying degrees throughout the globe. In Tanzania, for example, it's very common and is a driving force in their economy. At the same time, Africa is a fairly poorly-managed country, and funding is scarce. These animals are in desperate need of conservation programs in order to maintain the borders of their "pseudo-ecosystem", effectively one giant pasture surrounded by natural and man-made borders. They require a large and organized department of game wardens and wildlife biologists, to monitor populations, food sources, etc.. The funding for this comes exclusively from so-called "trophy hunting", and nowhere else.

As cliche and paradoxical as it may seem, these herds do in fact need their population managed. While the overall numbers may be low for, say, the continent of Africa, the herd health is largely driven by population density, not total numbers. Therefore, it is necessary for some of the animals to be removed from the herd. Simultaneously, due to the human-animal complex, it is necessary for the predator numbers to be lower, as well. This is an unfortunate circumstance, and is the fault of humans as a species, but it exists nonetheless.

So, they have a system set up wherein a select few older, non-breeding males are hunted for an outrageous price. I promise you these animals would be removed regardless, either by poachers or game wardens. So, they charge a high price for a tag to hunt these animals, therefore creating a giant funding source in order to pay for fencing, game wardens, anti-poaching departments, wildlife biologists, research, and all other materials and personnel required to maintain this ecosystem. People don't understand that these animals would be removed either way. Get that into your head. As Ted said, the Industrial Revolution and its consequences have been a disaster for the human race. In other words, humans, like beavers on steroids, have disrupted the entire collective of ecosystems to a degree beyond anything we've seen, and it's necessary to manage and conserve these ecosystems.