Well, to be fair, games kind of come with instruction manuals in-game now in the form of tutorials. I know it sucks, though. I remember C&C Tiberian Sun, whose instruction manual was the size of a laptop and gave you detailed information and backstories to all the characters, a lot of the units, the lore of the story, etc.
Personally, I love a good instruction manual, even if it's just something to read when I'm bored or waiting for the game to install (especially nowadays, am I right??).
I remember Dark Cloud 2's instruction manual which, intentionally or otherwise, smelled like a wax-sealed papyrus scroll.