It was a simpler time, it was a better time. Back in the black and white times of history, technology was at its infancy and the video cameras of that day weren't quite as efficient as what we have nowadays.

Early in the 20th century the video cameras used for filming recorded at lower speeds, usually 16 frames per second (fps). This meant that 16 still frames were recorded for every second that passed. The films were then shown to audiences using a 16fps projector. Today when we see the videos play, they run not at 16fps, but at 24fps, so instead of having 16 frames taking up a full second of time, it's compressed to .67 seconds which gives the illusion of a sped up film. Another way to think of it is 1.5 seconds of footage being shown in 1 second.

Here's an example of what old footage looks like.

It was not until the 1920s that this changed when audio began being added to movies. While video footage was tolerable to watch at 16fps, audio at 16fps was too split up. The solution was to up the recording speed of the equipment to a level where audio quality would not be affected, and this is why we now record at 24 fps.