Every Star Trek series was shot on film (35mm), it was only edited on tape at the time for the sake of the visual effects. They then rescanned all of the film elements for the HD versions. Widescreen =/= film. Those are not related things. No show at that time was shot in widescreen, whether it was on tape or film.
I actually hate seeing Seinfeld on TV in 16x9 because that's not how it was originally shot or intended at all, so it's artistically compromised, with heads cropped too close to the top of frame etc. The remastered TOS on TV is even worse. Unwatchable. They could just as easily have put the new TNG in widescreen (and may even still crop it for new TV broadcasts as they did for TOS and Seinfeld), but luckily stuck to how it was supposed to be. That was a huge concern I had with them remastering the show in HD.
I wish people didn't have this strange mental block that widescreen is always better, even when it destroys the integrity of the art. If it wasn't shot in widescreen, it shouldn't be widescreen.
Thanks for the lesson on film/video. I'm not sure where I heard/saw/imagined what I thought was true about the formats.
I'm going to have to take a closer look at Seinfeld cuz it doesn't look cropped but maybe I'm cherry-picking the "HD" episodes/scenes and not really thinking about it but they look great to me.
The "strange mental block" that 16:9 is always better comment is interesting, the keyword being "always". Taking 4:3 and zoom-cropping it to 16:9, yeah, that's not so cool, but seeing Family Guy and Simpsons switch to 16:9 as of a few years ago has been a hugely refreshing upgrade but I wouldn't want to go back and blow up older episodes though.
So, for me, 16:9 (or wider) is the way things should be made now, and they are, but taking old 4:3 stuff and zoom-cropping it isn't the way to go.