**Back in my day** (growing up in the 60s and 70s), when we only had 6 TV channels, just about every previously made TV show and movie were on constant rerun on the secondary channels. So, there was a lot of "before my time" TV and movies being consumed. Thus, I was fully aware of my parents' and grandparents' cultural milieu.
I can't imagine with how much content has been made since and is being churned out currently in a tsunami of content how any youth today would know about what were the cultural touchstones of previous eras except for those few movie or TV shows that have remained popular (like Star Wars, which is now 40 years old).