There is a balance that needs to be achieved here. I live in the Uk and the ( excellent ) NHS tends to go the other way, hoping for the best. Each procedure costs money and so doctors are reluctant to act unless there is clear evidence of illness. Money is at the heart of both issues. Taxes pay for healthcare here, and so governments are averse to seeming to be wasteful. As I understand it in USA, the drug companies are very keen to medicalise conditions so that they can increase their revenue streams. In his book, The Noble Lie, Gary Greenberg questions the actual medical causes behind conditions like addiction and some psychological illnesses. Is sex addiction an illness? and when was that defined as such? who profits from this diagnosis?
I don't suggest a big conspiracy at this point, more an alignment of interests. Drug companies want to increase profits. If they successfully cure all disease, then they will go bust. So they find more diseases. Doctors are in a similar position. They need to offer the latest cure for the latest diseases to market themselves ahead of the curve. And then there are the lawyers, offering to sue any doctor who doesn't find what ever it is the patient may or may not suffer from. Meanwhile, this allows the insurance companies to up the payments, putting greater pressure on companies and employment, while not actually making much difference to public health. The conspiracy comes when all interested groups come together to try to stop improvement or change.
George Bernard Shaw once said that professions are a conspiracy against the laity. I think you can argue that this is a good example.