Copyright law has a long history ported from earlier media. People here want to say media is just some product but the US decided that is in no way true.
The nuance that most people miss is that prior to about the 1960s, books were effectively uncopyable on anything resembling scale. The only options would be to either copy it out in long hand in pen, or on a more industrial level to create new printing plates from scratch, resetting the entire thing character by character. You also wouldn't easily be able to replicate things like photographs or drawings.
It was only with the advent of toner based xerox in the 70s that photocopying books became vaguely practical, but still cost about 5 cents a page, at a time when a mass market paperback might cost $1.25.
It was only with the advent of toner based xerox in the 70s that photocopying books became vaguely practical, but still cost about 5 cents a page, at a time when a mass market paperback might cost $1.25.