You didn't just read the Baldur’s Gate manual; you studied the spell descriptions during a thunderstorm because your parents needed the phone line. You didn't just reference the X-Wing manual; you memorized the shield configurations while eating a bowl of cereal before school.
Furthermore, many DRM protection wheels and cipher wheels are impossible to use digitally without printing them out. The physical manual was a tactile relationship. Because these manuals were often thrown away, lost, or recycled, pristine copies are rare. A complete "Big Box" copy of System Shock with its glossy manual sells for over $500. Ultima Online Charter Edition manuals (complete with a pin and cloth map) fetch $300. dos game manuals
In the floppy disk era, copying a game was trivial. Publishers needed a way to ensure you actually bought the box. Enter the manual. Games like Monkey Island 2 , King’s Quest VI , and Space Quest IV would boot up, display a spinning wheel of symbols or a grid of runes, and demand: "What is the 3rd word on the 14th line of page 27?" You didn't just read the Baldur’s Gate manual;