Why does this keep happening?

Bah. This is weak. Try the real world stuff: https://en.wikipedia.org/wiki/Unit_731

Unit 731 was responsible for some of the most notorious war crimes committed by the Japanese armed forces. It routinely conducted tests on people who were dehumanized and internally referred to as "logs". Experiments included disease injections, controlled dehydration, biological weapons testing, hypobaric pressure chamber testing, vivisection, organ procurement, amputation, and standard weapons testing. Victims included not only kidnapped men, women (including pregnant women) and children but also babies born from the systemic rape perpetrated by the staff inside the compound.