> Genuine question: why is this a problem if the publisher doesn't want a third party to use their work without their permission, or at all?

Suppose the publisher's content consists of slander or government propaganda. They use DRM to prevent copying or archiving or citing it properly, and revise it as they wish, denying that older versions were ever published.

In the print days, you'd still have the old copy. Today, you can point to the internet archive. What if the text was DRM'd?

What the publisher wants to permit is one consideration. What the reader has a right to do with what they're reading is another.