Although manuals may seem unnecessary for purchase with the game, it does give a fill of completeness to the whole package. In addition, some manuals(notably more 8-16 bit stuff) have official artwork in it without having to buy a supplement art book to see a glimpse of game design art. The manuals serve to complete the whole CIB package most of the time( and for imports, spine cards I feel aren't really necessary for a cib as much as manuals since its not too important to my eyes).
