The Saturn V was the first and second stage of the system that sent humans to the moon as part of the Apollo program, that's why a huge number of people knew about it. I'm not sure what you mean by "an age thing" (are you too young? too old?), but it's in the "current" paper copy encyclopedias (most even have images) that I assume most schools still have, and encyclopedias from the 1980s and 1990s appear to as well, so it's not just a 1970s thing.