After thinking about this more, I believe that some of the answer is whether the copyrighted material is art or craft. I would define art as a creation where the form is more important than the function, and conversely craft as something where the function is more important than the form.

Clearly, there's an analog scale between these two poles. But, take for a moment an http request library. Given a certain spec, multiple programmers (or teams of programmers) might take different approaches to meet that spec -- but the result is functionally the same, and if they faithfully follow the spec, they are all going to be more or less interchangeable.

I think a photograph is qualitatively different. If I were to ask a photographer to "take a picture of an ant", I could get radically different results that are not interchangeable.

I know I'm not going to convince you, so I'm not going to keep trying, but I think abolishing copyright would provide a dire challenge to people who create visual art for a living.