According to a survey from Drug and Therapeutic Bulletin, many doctors are not very well informed on the subject of herbal medicines, and many don't want to be.
Doctors are not trained in alternative medicine in medical school, and many seem to be disinterested in learning more. Many do not choose to look into what if any herbal treatments their patients may be taking. And some doctors who are interested would simply browse the internet for their information, with no guidance as to how to know if that information is valid or not.
Michael McIntyre, chair of the European Herbal Practitioners Association, suggests that many doctors feel that herbal medicines are a step backward, and doubt their efficacy.
"In the Drug and Therapeutic Bulletin survey, 75.3% of physicians thought herbal medicines were helpful in some circumstances, but an equally high proportion said that the general public has misplaced faith in these compounds (71.8%)."
http://www.kevinmd.com/blog/2010/04/alternative-medicine-taught-doctors-medical-school.html