> Not everyone does (pregnant or nursing women, or the sick, for example), and not everyone fasts for that period of time. Some people in different roles in the church (what non-Mormons might call a prophetic / visionary role) are encouraged to fast more often.

Indeed. I wanted to put that in my initial comment, and forgot. If you are sick, pregnant, or there are other health concerns, or doctor's orders to prevent you from fasting, then you don't.

Also, you are encouraged to fast more frequently for spiritual matters indeed.