[tompccs]

Old film was less sensitive, so it needed longer exposure time. Film was therefore cranked slowly to avoid under-exposure. During playback, it was generally preferred to run the film slightly quickly than to have a lower frame-rate (which would have made motion jerky)

[V-2]

It doesn't really appear that jerky after being slowed down. My taste apparently differs from people's in the past, since I'd rather have it that way than sped up...