This is news? Denver must be behind the times. We had weapons lockers within spitting distance of all of our checkpoints where I worked.

Airports have a lot of square footage under roof. It doesn't make sense for LEOs to walk around with shotguns and ARs. So you pick an area that's easy to access (say, a checkpoint), and turn one of the closets into a weapons locker. That way, in the event something really terrible goes down, a responder can get properly armed/armored on the way to the scene.

If you think DEN is installing those to protect TSOs or enforce TSA mandate, your organization REALLY has delusions of grandeur.