MI is difficult to install. It requires specific tools and talent.
It is, however, able to tolerate conditions that devastate all other conductors.
My personal favorite is motor leads to sewage pumps in a water treatment facility. Nickel coated MI can stand the vapors.
The other obvious need is where it's very hot or could be very hot: steel mills, rocketry, emergency circuits, nuclear power systems, and such.
All of which I'll never get involved with.