The medical establishment that I have familiarity with (in the US) pretty much only ever treats symptoms, not causes.

Don't believe me? Next time you go to see your primary care physician, ask them what you should be doing to lower your risk of whatever malady tends to run in your family. (Diabetes, cancer, dementia, etc.) They're going to stare at you in blank confusion for a few seconds before making some vague suggestion about a better diet and more exercise. Guaranteed.

The reasons are many, and detailed enough to write MANY books about, but the low hanging fruit is: we don't have a culture of monitoring and improving our own individual health, physicians are trained almost exclusively to solve problems not prevent them, modern nutrition science is a joke, omnipresent health insurance distorts incentives for everyone, doctors are too overworked to get to know their patients, private equity has captured a large chunk of health care, drugs are positioned as the first line of treatment for almost everything, etc.

In my experience that’s wildly inaccurate. Dietary choices, weight loss, exercise, etc are often given as an effective means of avoiding and or controlling a wide range of conditions.

People are instead blowing off such advice because they don’t want to hear it.

Everyone pretty much knows how to be healthy- good diet (leafy greens, abstain frand exercise. Diets, fads, etc are all just ways people sidestep being slightly uncomfortable rather than limit what they eat and do. Lots of societal things male it harder, eg hyper-palatable foods/ads/overworked/food availability, but that’s the long and short of the root cause.