Basically, 9-1-1 Dispatch relies on the fact that it's a grievous crime and very unglamorous to make a fake report or troll the operator. 9-1-1 needs to remain as credulous as possible, and err on the side of false positives, lest they gain a negative public image.

At the same time, it costs nothing to pick up the phone and prank them. Any actor from anywhere could do it, and outside their jurisdiction, what can they do? The dispatcher is not empowered or equipped to discern truth from lies over a mere voice line from a stranger. The dispatcher can't even run a CAPTCHA to trap AIs. The public absolutely relies on being believed when they sincerely call that same voice line.

I do, perversely, see the merit in repeated response that simply turns out to be a drill. The merit is both training and public image, if the militarized police want to instill fear and shock and awe in that neighborhood, or on the evening news, then they get it by responding, not by dismissing obvious fakes. How often do you get to test your flash-bang rifle, fire up your bomb-siege-robots, and put a few miles on your urban tanks? It's like a parade on your wedding day.

Only thing is, there seems to be no financial incentive or reward for the SWATter. Unless SWATting could be used to tie up and distract law enforcement resources as part of a bigger conspiracy, the only endgame of SWATting seems to be a drain on resources.