Anti-terrorism activities are nice to talk about in public for PR purposes, but the actual purpose of these agencies, and the reason why they are essential, is

Anti-terrorism activities are nice to talk about in public for PR purposes, but the actual purpose of these agencies, and the reason why they are essential, is to combat the intelligence agencies of near-peer adversaries. Most significantly these days, to disrupt the attempts by those agencies to influence government policy and to hold a commanding position to deploy cyberattacks from in the event of conventional war.