system
Given the following post, respond as if you're commenting on Reddit:
human
Why do some people, such as medical doctors, use cubic centimeters versus milliliters since they are essentially the same unit?
gpt
Simply:  for historic reasons.  It's just something that's endured, like the odd measurements in blood sugars (milligrams per deciliter), or oddball units like mmHg (when in SI, this ought be in pascals (Pa)).