Are you talking about real doc work? Or narrative stuff. Because in my experience in the doc world, lighting has to be very selective. Of course I'm lighting interviews, and anything I can. But in the world of fast moving subjects and spur of the moment things happening, it is so incredibly handy to have a camera I can crank up the ISO and get a decent image when the character is only lit by the light on the stove, or the dash lights in their car, or the stars in the desert.
I totally get it that knowing how to light is much more important than having high ISO, but that doesn't negate how important it can be for doc work. I guess this all totally depends on the use case though.