As a sibling comment pointed out, the medical community consider prevention part of the medical system. It took me a while to understand what I thought was some weird (and potentially intrusive[1]) behavior of some doctors/clinics that they indeed do feel it is within their purview.

Not just discussions with a patient, but advising the government, pushing for regulation on things related to obesity, working with schools, etc.

Arguably, the problem in the US isn't that these are outside the control of the medical system, but that most Americans believe they should be outside the control of the medical system.

In (some) other countries, your comment would be a real "WTF?"

[1] Throwing in questions like "Is there a firearm in your house?" and "Is there a swimming pool in your house" intermixed with "normal" medical questions.