Earlier quoted context omitted.
Why would you do that? What an awful idea. People made those shows in the 4:3 format, you’d just be adding fluff. This is like adding more description to a book so it becomes an epic novel instead of a novella. I’d say keep to the creators intent…
I'm not the person who suggested it, but I wouldn't mind having it fill my (wide)screen when watching. That said, I understand that some film/tv uses the frame very precisely, however I'm not sure that these two particular examples do that throughout their entire episodes. (Though I bet that in Seinfeld in particular it might weaken/ruin a few visual gags.)
Do the black bars actually bother you that much? You know there are cropped 16:9 widescreen versions of some of these shows (which I personally detest, but I work in the business of moving images).
Genuinely interested in why this bothers people.