Conservative excisional surgical therapy for endometriosis is not covered well in many residency programs. One reason, particularly in countries with a privatized health care system, is that endometriosis is not seen as commonly in medical school hospitals as it is in private practice, so there is less clinical material available. The importance of private practitioners in the study of endometriosis has been well accepted since the time of Sampson in the 1920s, himself a private practitioner.
Another reason conservative surgery is not taught is that endometriosis is considered to be a progressively spreading disease, a consequence of the theory of tubal regurgitation and implantation of viable endometrium. If endometriosis does become more widely distributed in the pelvis as women get older, then, indeed, surgical removal of the disease would seem futile because "it will just come back." With this mindset, it is natural for physicians and patients to avoid surgery and resort to medical therapy.