what is the design problem with that copier?

I was studying ethnography and interaction design. That's when I got to watch this video. Ethnography and the PARC Copier

While searching for the source of that video, I found that the video created by Lucy Suchman about the ethnography research. Lucy Suchman conducted an ethnographic study of copy machine use in the workplace. And she did make a video.

I found out from watching the video that this video is related to the ethnographic study, and the people in it found it very difficult to operate the copier besides they were computer scientists and a Ph.D. student during that time.

What I don't understand is why they are struggling to run that copier? How does that relate to design? What exactly is the problem with that copier?

But, this is not related to my homework this came out of my curiosity when I am studying the design.