Roughly the same age as you have to be to understand The Maxwell Car.  

The one with the Mel Blanc engine.

I think the generational thing is that people of the Boomer generation went back to look at popular culture to a generation or two before. Many of us knew movies from the silent era forward, and were familiar with old time radio shows.
I think later generations were not as interested in the past.
It's like when they show a dial phone or VHS machine and younger people don't know what it is. We were long past wash boards, hand crank phones and gramophones, but I could recognize them.

And the answer is, "That's great Doc, I couldn't play the Piano before."

Well, also, before you had so many options, syndication packages tended to be for programming and movies at least 10-20 years old.  Anything newer was either on network or wasn't likely to find a buyer, for a bit.  By the 80s, with cable expansion, you could sell programs to other channels, as well as syndication, so there were more buyers of content and the production companies started putting older episodes into syndication offers, much earlier than in past.  So, syndication turned into more and more recent programming and older material was more often sold to cable channels.  Then, you started to get more and more narrow focused channels, with stuff like TV Land and ME TV, where they were aiming at a specific demographic.  Same with movies.  They used to be offered in syndication packages, but tended to be from 10-20 years or more, before.  Anything newer was likely sold to the networks for broadcasting.  The older the film, the more likely it was to show up in cheaper syndication packages, apart from time-honored classics.  Again, with cable, the older material moved to cable channels and then into more specific themed packages, like Encore Westerns or similar.  new stuff hit the movie channels first, then the networks, then syndication.

Technology has changed rapidly with the introduction of micro-processors and other digital technology, which allowed for rapid research and development and deployment in consumer products.  Plus, planned obsolescence meant older technology wasn't around homes as long.  So, younger and younger generations are encountering the information and technology of the past the same way we did (I'm Gen X, but right near the start, while my older brother is at the end of the Baby Boomers).  My grandparents had all kinds of older machines and appliances around the home (especially my paternal grandparents, who lived on a farm) which allowed us to see them work.  My grandfather's tractors were hand cranked, to start, and he milked his dairy cow by hand.  They had a party line, because they were in a very rural area, in southern Illinois, pretty far away from any city.

Pop culture has a shorter life span, now, because of all of the choices for delivery.  When you had a couple of national radio networks, you heard the same programming, aside from the regional-specific stuff.  same, when television started.  That remained mostly true into the 70s.  From the 80s on, you get more alternatives and the pace speeds up.  Look at movies.  They would stick around far longer, in theaters, because the studios didn't produce as many films, in a year; plus, you had fewer theaters competing, in markets and didn't have multiplexes.  Again, a lot of that changed in the 80s, as you had more independent production companies, more distributors, more theater chains, with more screens per theater.  Competition increased and the drive was to have the latest movies, to draw the bigger crowds.  Star Wars was held over in theaters through most of 1977 and even into 1978, in some areas.  When was the last time you saw a theater market something as "held over?"

I lament the fact that entire shows , music genres and movies are vanishing from memory. Maybe we have too many Channels available and no one is interested in even trying reruns of Columbo or Law and Order. 

That's my understanding as well. Based on other forums in which I occasionally post, I've also learned that there are quite a few people in the late 20s through early 40s age bracket who really like Columbo.