The NoScript tag is rarely used these days.
Sites also used text within a NoScript tag to give an accurate description or transcript of the contents contained inside the non-HTML based program. This helped to inform a user of the contents of the video, while also giving the same information to search engines. For instance, a NoScript might read “video showing a dog chasing a squirrel”.
In a nutshell, it did for video content and other dynamic content what the alt tag does for images, but is now more or less redundant.