Copyright information "allows the owner to protect against others copying or reproducing their work. If you create something you should be able to control what people can do with it". We are all creative in our own ways and that's how it needs to be, so therefore we don't want someone stealing our work because they need to be creative and come up with their own.
Copyright Facts for Kids (kiddle.co)
YouTube Copyright School - YouTube
Fair Use "is a doctrine in the law of the United States permits limited use of Copyrighted material without having to first acquire permission from the copyright holder". Basically what this is saying is that someone can use part of their work but not all of it.
Creativity, Copyright, and Fair Use - YouTube