Probably cost as compared to insulated cable assembly of equivalent ampacity and flexibility.
Braid is very flexible so it will have a long service life, since it is braided rather that just laid up like a rope, (uninsulated fine-strand wire would unlay in production or use) you needn't pay to insulate it, you dont need failure prone terminals in many cases, and it is compact.
Just some guesses based on my past working life in the wire and cable industry.
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-- Dave
Pics of my '73 project here:
http://members.tripod.com/mike4g/dds73_b4pics.htm