That no matter how objective scientists pretend to be, there are often ulterior motives working, consciously and unconsciously. Drug manufacturers pay researchers to confirm a drug's effectiveness. If the researcher fails to find the effectiveness, that researcher is all but cut off from future funding opportunities and studies by that drug company. Science can be objective. But humans conduct science and humans are notoriously subjective.
Humans also have to interpret the science and data, which can lead to further errors.
Only after a drug has been out on the market and approved by the FDA do truly independent researchers, who have no direct financial incentives to find a drug effective or ineffective, get a crack at the investigation. Sometimes such researchers find somewhat disturbing results, such as those reported in the NEJM issue. And drug companies are not alone in this. Psychologists who spend their lives pursuing a particular theory or idea about how behavior works in people also have an incentive to find the results they are seeking. None that I know of can do this.