Whenever you assume the innate goodness of someone overrides their natural desire to earn money, you end up with a problem. With doctors, having to legislate the gifts received from pharmaceutical companies is an obvious counterpoint to the idea that the vast majority of doctors are 100% ethical and only make choices for health reasons. Clearly a lot of them were influenced by pharma money.
A second thing your statement supposes, is that people prescribing drugs in first-line care have the same agenda as people doing medical politics, or at least are not concerned about the well-being of their patients. Every profession has its black sheep, but I think you severely underestimate the drive docs have to see their patients do well, and the self-esteem hit we get when things go wrong.