Answer: Because Foucault did not try to reach an ultimate historical truth but tried to explain the various transitions in the past.
Michel Foucault, a French historian, felt that explaining transitions in history is more important than arranging events chronologically. Like an archaeologist uncovering layers, he analysed how knowledge changed. He also studied areas ignored by historians, such as psychological disorders, medicine and prison administration. Hence he called his method ‘the archaeology of knowledge’.