Fully processed color and B&W films have less turbidity than unprocessed film due to the emulsions themselves. Fully opaque films use a rem jet backing to prevent antihalation, but other films are just cloudy until processed. Opacity is also caused by the presence of dyes which sharpen films by reducing internal reflections caused by the emulsion grains acting as tiny mirrors.

This is much more complex than the average person thinks, but basically, all of the materials that cause this effect are removed at the end of the process.