Hello!
1. The hardest part of creating CGI images are the tools used to create them. According to the internet, "CGI is created by visual artists also called 3D artists using various painting/ modeling/ animating and compositing tools." Sometimes, people may not have these tools. It is sometimes hard to find the compositing tools and the other tools too.
2. When a person creates something, they now basically own it, if they made it all by themselves and did not plagiarize or etc.. Without intellectual property rights, artists would be able to steal other artists work, and stamp it as their own work. This would not be fair to the original artist, because he/she gets no credit for the workpiece.
Hope this helps, have an awesome day/night! :)