If you plan to earn a salary in computer science, you or someone will have to find customers to pay for what you create. If technology allows unlimited perfect copies to be made of your creation, and the customers see it as perfectly ethical to use these copies without paying for them, it seems like a non-trivial problem to keep you in work. (I work in IT, and I "make unauthorized copies" of content like books and music. I think it's usually wrong.)Intellectual property is a bullshit notion. I do not deny you a file by making a copy of it.
You are not denying me anything, but you are denying something to the content creator: compensation for the work of creation according to the terms by which that person made (or intended to make) the content available to you.