Traditionally, movie theaters showed each analog film frame two or three times, so the flicker would be 48Hz or 72Hz, not 24Hz. 24Hz flicker is very obvious and

Traditionally, movie theaters showed each analog film frame two or three times, so the flicker would be 48Hz or 72Hz, not 24Hz. 24Hz flicker is very obvious and annoying to everybody. Digital projectors might sample-and-hold like LCD displays and therefore have no flicker despite the low framerate. See https://en.wikipedia.org/wiki/Movie_projector#Shutter https://en.wikipedia.org/wiki/Movie_projector#Shutter