Because the decision to serve is a personal decision. People come home for a variety of reasons (sometimes by choice, sometimes not). Regardless of the reason, it is not the business of people who are not friends or family to speculate. A missionary may choose to share the information that he/she wants to share.

I personally admire Chaz for his desire to serve and for whatever service he rendered. Coming home early is not easy (regardless of the reason). Speculation is not helpful and participating in discussions that would lead to speculation is not helpful.