Maybe because 99% of people think the ones being "Gangstalked" really are just untreated paranoids. The most compelling evidence that it is happening is the screams of "enjoy your high, narcissist!" when you ask for any real evidence that isn't just people saying that it's happening. Which is not very compelling.  And I'm not sure why it constantly gets lumped in with narcissist abuse. They're orders of magnitude apart. Some sort of "credibility by association" fallacy?