My favourite variant of this was F-19 Stealth Fighter asking you to do aircraft identification, which you could get from the manual .. or any library book on US warplanes.
Least favourite was some game (TMNT?) which printed the codes in gloss black on matte black.
It wouldn't be out of place in a library.
Not that I turned that knowledge into good results but that's another topic.
What a delight that game and its manual were.
They weren't license keys, persey, as all the printed material was the same, but a tacit test as to whether you had bought the actual game, or just copied the disk.
They were multiple choice and some of them were very tongue-in-cheek, like Richard Nixon was an “audio technician or plumber’s friend”.
We live in a completely different world now. Imagine: you just bought a game, that was probably not cheap, and you won't play it because it requires opening a printed booklet you got with installation media and already have next to you? Sounds unlikely, especially since you already went through the trouble of going/driving to a physical store and installing the game (often from multiple cds/floppies, and it often took a long time). And it's not like you had a choice - another game was another drive away, and there were no refunds.
And yeah, we were younger.
Today we live in a world of constant connectivity and instant gratification. It's a better world, but a little nostalgia won't hurt