It seems to me that doctors have such an issue giving a straight answer to what one would consider an otherwise direct question. I understand that many occurrences of this "syndrome," perhaps as high as 50%, are related to the fact that professional, ethical and liability issues are associated with much of the subject matter.
However 20 to 25% seems to applicable to the "not having a freakin clue and can't risk any sort of credibility category," leaving the remaining 25 to 30% simply habitual speaking patterns.