Well i know in the modern Era they used super35 a lot for budgetary reasons. Like on Star Trek VI but II was shot in scope.
The Lord of the Rings trilogy was shot in super35 but then cropped to 2:35:1 ratio. Like Star Trek VI in the theatrical version.
In the Sixties/seventies they often used Techniscope because it was cheap too. I know It was used on a movie Kurtz worked on prior to working with Lucas, as well as on Graffiti and THX. Oh and Sergio Leone used it in the dollars trilogy.