At some point they do it because they are doing it. In other words they learned to regurgitate some basic "War On Terror" lines when asked about they are doing it, but really they do it because there are jobs, resources, servers, infrastructure, support, billable hours, resumes, training, sunk into doing it. And stopping it is just not profitable.
They can never make that as the official reason (although, for example, the private prison lobbyists are not shy about why they advocate for maintaining War on Drugs, it is simply bottom lines for their clients). Here it might one layer lower, on top wrapped in some idealistic War On Terror / Keeping Americans Safe rhetoric. But almost everyone in the chain knows it is about just keep going.