Its because they're not what people want to imagine (hypercompetent ubermenchen who they're outsmarting) but just covering up "mundane" though still devestating crimes.
I wouldn't classify putting LSD in the water supply to be "mundane".
Neither would I classify MK-Ulta that way: "Techniques included the covert administration of high doses of psychoactive drugs (especially LSD) and other chemicals, electroshocks, hypnosis, sensory deprivation, isolation, verbal and sexual abuse, as well as other forms of torture."
Or the releasing of biological weapons (MK-Naomi): "at least three covert techniques for attacking and poisoning crops that had been examined under field conditions."
Or Operation Notherwoods: "to both stage and actually commit acts of terrorism against American military and civilian targets, blaming them on the Cuban government, and using it to justify a war against Cuba."
Or the Tuskegee experiment: "The purpose of this study was to observe the natural history of untreated syphilis; the African American men in the study were only told they were receiving free health care from the Federal government of the United States."