That choice was made long before Scorsese made The Godfather; and so has virtually every other movie made over the past century.

Real artists understand the limits of the medium they're working in and shape their creations to exist within it. So even if there was no artistic or technical merit in the choice to standardize on 24 FPS, the choice to standardize on 24 FPS shaped the media that came after it. Which means it's gained merit it didn't have when it was initially standardized upon.