Physical Danger
Air traffic controlling is not a dangerous job. It's all about creating a safe environment for yourself and others. Sure, you make sure planes don't crash into you, but there are physical requirements to maintain as well.
Air traffic controllers have gotta stay in shape. They need to have 20/20 vision, show no signs of heart disease, retain healthy blood pressure, and have no history of mental health problems. You're pretty much mandated to stay healthy to keep your job.