alt Hacker NewsNot saying it had anything to do with X-files, but also when you shot something for TV but were not entirely sure if the capture would ever go to the movies, you protected the wide frame.
Also, if you shot a movie but wanted it to look good in TV later, you put the most important action somewhere in a 4:3.
Some movies were shot in 4:3 (ish) and cropped in the theater. Titanic is an example.
(For the pedantic, yes there is a name for this technique, and yes the ratios aren't exactly 4:3.)