Watching old sitcoms over and over is...

What you do when you don't actually have time to watch shows and can't be expected to follow along to storylines. The shows you mentioned require you to be fully invested in watching it, which is awesome when you have the time to do that.

But when you are having to constantly leave and return to shows without being able to pause them, running after kids, or you just want to zone out without having to think about anything that is when old sitcoms come into play.

Personally I've dropped Netflix a long while ago and cycle through few services when I do have time to watch things and run my own server for most other things. But there is a large portion of the population who enjoy watching re-runs because it is mentally relaxing, you can turn off your brain and just enjoy. Really it's not too different from listening to the same music album over and over again.