> But is it the case that copies made for the purpose of using illegally obtained works are not infringing?

Well, the question here is "who made the copy?"

If you advertise in seedy locations that you will send Xeroxed copies of books by mail order, and I order one, and you then send me the copy I ordered, how many of us have committed a copyright violation?

Copyright law is literally about the copies. A xeroxed book is exactly one copy. Mailing and reading that book doesn't copy it any further. In contrast, you can't do anything with digital media without making another copy.

> "Who made the copy?"

This begs the question. With digital media everybody involved makes multiple copies.