Correlation does not imply causation is a cliche. Why do people constantly repeat this quotation without the obvious extension? What is causation and how is it

Correlation does not imply causation is a cliche. Why do people constantly repeat this quotation without the obvious extension? What is causation and how is it established? Seems pretty obvious, yet for some reason most people never ask this question or are even aware about how to establish it. They just say correlation doesn't equal causation and are suddenly psychologically frozen. Their biases prevent them from taking the obvious step forward. The experiment to establish causation is simple. Tape a magnet to your dogs head, observe if there are any differences in pooping behavior.