production sound vs. post-production sound

Why is there only one category called "Sound Department" rather than a separation between production sound and post-production sound? These two aspects are hugely different and each field contains a wide variety of unique job titles.

For instance:
Production Sound - Sound Mixer, Boom Operator, Sound Utility, A2, Playback Operator, Sound Recordist, etc.
Post-Production Sound - Supervising Sound Editor, Sound Designer, Dialogue Editor, ADR Recordist, Sound Effects Editor, Re-Recording Mixer, Foley Artist, etc.

Lumping all of these people together as the generic "Sound Department" is essentially the same as if the director of photography, camera assistants, editors, visual effects artists, colorists, etc. were all just referred to as "Picture Department."

To display credits in this way is not only confusing, but greatly ignorant of the actual filmmaking process (not to mention very dismissive to the crucial role these crew members play).