Oh, just like how Federal Agents are "God" and can carry firearms on airplanes, unlike you?Probably because of your employer.
ETA - I answered this while I was doing something else. After reading it again, I see I misread your post.
Still the answer is basically the same.
If one does not meet the medical requirements to get an exemption, he does not get one, unless he is a government employee because obviously government employees are God and they can see much better than everyone else. However, that medical exemption is still available to anyone, should they become unfortunate enough to need it and fortunate enough to actually be approved for it.