There may be a few "Rocky Horror Picture"-like shows or episodes that bear multiple almost cult-like viewing, but most people may watch a long-forgotten show one time again, but not more than once.
For example, I found that I had missed many episodes of N.Y.P.D. Blue and E.R. and discovered I have both free on Hulu, so I watched alllllllllll of them while working on my website. Lotta' fun, but just once.
I never watched Seinfeld when it was new as in my market it did not run when the show started and when I got to LA I found it did not relate at all to my culture, sense of humor or lifestyle. So, there are many "hit" shows that won't reach new people... and many of the old fans have no desire to see it again... even once.
And so much of network TV in recent decades has been non-scripted shows. Who want's to see old episodes of reality shows or re-runs of awards shows or, even, replays of decades old sporting events?
In fact, out of curiosity I'd love to see what kind of ratings a re-run of TV's biggest audience-getter, the Super Bowl (tm), would get?