My answer will be because poaching is a business. And this business moves millions of dollars in the world every year. In addition, it provides food and resources to thousands of people around the world, but it also seriously threatens the lives of millions of species and the balance of their ecosystems, among other problems.
Among the species threatened by this illegal negcocio are:
1. Mountain gorillas
2. White shark
3. The white rhinoceros, enter others.