Now clearly I'm not saying that doctors try to give bad diagnoses for profit (because they don't). But beyond a certain minimum bar, and on a purely financial basis, improving diagnostics or prescription accuracy doesn't not make a medical practice more money. And the responses here illustrte that.
Now, whether that's the right/wrong incentive strucgture is a whole 'nother discussion. And I personally can't think of something better than what we currently have - but it is a truth of the current system.