I think it's not about re-broadcasting, but about providing the show in a better format. The originals were shot on 35mm film, and then that was "mixed down" with the visual effects to some lower-definition format (maybe SVHS, but I'm just guessing) and the result sent to TV stations to broadcast.
To make a high-definition format (e.g., blu-ray or HD streaming) they'd go back to the original 35mm masters and re-convert them. But then all of the visual effects had to be re-added on top.
There are various articles that mention quality issues with the remastering:
To make a high-definition format (e.g., blu-ray or HD streaming) they'd go back to the original 35mm masters and re-convert them. But then all of the visual effects had to be re-added on top.
There are various articles that mention quality issues with the remastering:
http://trekcore.com/blog/2015/08/netflix-brings-vfx-fixes-to...
http://trekcore.com/blog/2012/11/review-star-trek-the-next-g...