It's not tigers per se, but the concept of keeping examples of all species in the wild. It promotes conservation of species, elimination of extinction of species. The reason we don't want species to go extinct is because we haven't yet figured out every possible beneficial use of every species. Many such beneficial uses are anticipated, though they cannot be predicted for any particular species. We've only just scratched the surface of the drugs that can be obtained from plants and animals. Besides, from aesthetic considerations, future generations will want to enjoy seeing animals in the wild, not just in a zoo. It is inspring, to say the least. And in the future, travel between the continents will be cheap and easy, compared to the previous centuries.