Some of us are 30 and definitely missed some of the shows in the top 200 so far. Mr rogers, la law, 90210...all before my time.
Do a lot of people only watch stuff when it originally aired? I mean, I wasn't alive when Get Smart aired but I watched it later and put it on my list. I assume people will have stuff like I Love Lucy or The Honeymooners on there despite not being alive for them, but maybe I'm over-estimating that.
I think a lot of these haven't had the same staying power. If it hasn't become something with a second life on Netflix or Hulu, I probably haven't seen it.
Take Friends though. That was definitely before my time, but it was extremely heavily syndicated so I'd seen it here and there...but then it was HUGE on Netflix. Im sure I love Lucy was too, but on the "old people" channels with MASH and other stuff I'm aware of but would never watch (isn't I Love Lucy black and white?).
Something like the Office was similar - I don't think I know anyone who saw it actually air live but almost everyone I know has seen it end to end streaming.