The value in the works. If people are copying them then presumably they find then beneficial in some way. Maybe they're entertaining. Maybe they're informative. Maybe they're useful tools.
Whatever actual value the works have comes from the people who create them. It wouldn't exist otherwise. We can debate the economics around compensating those people (or not) but the fact that all of the value originates with the creators is objective and undeniable.
As I've commented elsewhere in this discussion, there are some legitimate concerns about scope creep and having copyright maximalists making the laws, but that doesn't mean everyone, or even most people, making copyrighted works or relying on copyright protection as a basis for creative industries has somehow broken the implicit bargain that copyright represents.
Likewise, someone posting the same few examples of people who have been successful in other ways every time this debate comes up doesn't change the fact that by far the majority of our commercially created works today are supported by copyright one way or another (as, for that matter, are most open source or community-licensed works). Show me the high school math textbook that experts spent two years writing that was funded by some other means, or the business admin software, or basically anything that is useful but not necessarily enjoyable to create. Or just look at the production values of fan fiction, amateur videos, hobbyists computer games, or band recordings made in their garage because they couldn't afford a studio.