Most hysterectomy operations also include removal of ovaries and this practice is going on for decades and probably no one knows who started this practice. The rational which is kept forward for removal of ovaries is that it will eliminate the risk of developing ovarian cancer.
Now the issue is, it’s not necessarily that every woman will develop an ovary cancer so the simultaneous removal practice of ovary with uterus might be challenged. Interestingly new studies bringing in a very interesting and important piece of information that by removal of the ovaries although a woman can be rescued from ovarian cancer occurrence in future but removal of ovary might be pushing women to many other causes of death like heart disease, colorectal cancer and lung cancer. Probably odds of dying from these other diseases are more than dying from an ovarian cancer in women who don’t have any genetic susceptibility to develop an ovarian cancer.
So if you are planning a hysterectomy talk with your doctor and understand both the pros and cons of removal of ovaries unnecessarily.
Probably chopping a specific diseased trunk of a tree is better than removing the whole tree unless the whole tree is prone to the disease!
References- http://journals.lww.com/greenjournal/Fulltext/2013/04000/Long_Term_Mortality_Associated_With_Oophorectomy.4.aspx, http://www.nlm.nih.gov/medlineplus/news/fullstory_135220.html