The title is a sort of a joke of course. The real reason is that the drugs that are being tested are ineffective in the vast majority of cases (92%). Before public resgiration of clinical trials became mandatory, majority of the trials reported positive results. Now, think about all the drugs that you or people you know take on a regular basis and were approved based on trials prior to year 2000...
Likelihood of Null Effects of Large NHLBI Clinical Trials Has Increased over Time
"...We identified all large NHLBI supported RCTs between 1970 and 2012 evaluating drugs or dietary supplements for the treatment or prevention of cardiovascular disease. 17 of 30 studies (57%) published prior to 2000 showed a significant benefit of intervention on the primary outcome in comparison to only 2 among the 25 (8%) trials published after 2000 (χ2=12.2,df= 1, p=0.0005). There has been no change in the proportion of trials that compared treatment to placebo versus active comparator. Industry co-sponsorship was unrelated to the probability of reporting a significant benefit. Pre-registration in clinical trials.gov was strongly associated with the trend toward null findings."
Preregistration of clinical trials causes medicines to stop working! - Chris Blattman
Likelihood of Null Effects of Large NHLBI Clinical Trials Has Increased over Time
"...We identified all large NHLBI supported RCTs between 1970 and 2012 evaluating drugs or dietary supplements for the treatment or prevention of cardiovascular disease. 17 of 30 studies (57%) published prior to 2000 showed a significant benefit of intervention on the primary outcome in comparison to only 2 among the 25 (8%) trials published after 2000 (χ2=12.2,df= 1, p=0.0005). There has been no change in the proportion of trials that compared treatment to placebo versus active comparator. Industry co-sponsorship was unrelated to the probability of reporting a significant benefit. Pre-registration in clinical trials.gov was strongly associated with the trend toward null findings."
Preregistration of clinical trials causes medicines to stop working! - Chris Blattman