The most common oath taken by doctors includes:
"I will not permit considerations of age, disease or disability, creed, ethnic origin, gender, nationality, political affiliation, race, sexual orientation, social standing or any other factor to intervene between my duty and my patient."
"The health of my patient will be my first consideration."
http://en.wikipedia.org/wiki/Declaration_of_GenevaThus
Tradition.
Cultural momentum.
religious traditions
Are irrelevant, because these are not in their job description and additionally, most doctors even explicitly denounce such things as barriers or obstacles to promotion of patient health.
Father is circumcised so the kid should be is the "obvious answer."
If my father lost his leg in Vietnam, should I also be expected to amputate my leg out of family tradition?
In addition to also not being a valid professional concern by oath like the other things, the logic of this in particular is especially silly.
It's always been done and a lot of people believe it's beneficial.
Presumably doctors are literate to have gotten through medical school, and have the ability and education to read, you know, studies, not ancient traditional beliefs as the basis of their medical understanding.
This doesn't stand up for a second as a convincing explanation of why doctors actually perform these procedures. They know full well it isn't beneficial.
Which still leaves profit as pretty much the only slightly believable motive to me for why it actually happens.
But regardless, for purposes of this thread, even if some of the other things listed do contribute partially, they are still ALSO good reasons to not treat the advice of professionals as sacrosanct by default. If doctors are basing medical decisions on "cultural tradition" etc., that's just yet another great reason why people shouldn't be just doing whatever they say in spite of their own research.