Maybe they signed up for Iraq in a fit of patriotism to defend our country and then got their ass bombed or some other thing and now are disabled. Maybe they were a fire fighter and then went and helped to save people from the world trade towers and then breathe the terrible air and then got disabled.
People become disabled, not everyone was born disabled. It's people like you that cause people who do get disabled to feel ashamed because they no longer contribute to society.
Beware of the Turing Tar-pit in which everything is possible but nothing of interest is easy.