Often a burn accident involves the negligence of another party. They contract out about 300 hours of programming each year. This form of writing is primarily historical retrieval for the narration. The shows are primarily clip driven with very little additional shooting. Mostly it is just the occasional interview to spice up the otherwise repetition of clip after clip.
Somebody has to do that writing.
In many cases, a documentary writer is much like an investigative reporter. Digging up information, finding clues to solve mysteries, and finding missing persons are all messy jobs writers might find themselves doing. This can be really exciting, especially since oftentimes, the truth we discover is stranger than fiction. Stranger even than our wildest imagination. IMAX documentaries like the one on the oil fires of Kuwait, the moon walks, Sahara, etc.