For the first 2 years, i would religiously put them out on every job. Then I would have the idiots on their phones, tripping over the huge warning cones (the yellow ones with rubber bases) and thought, whats the point.
The hose i use is bright green and can not be missed unless they are blind. I simply make sure that I have no loops in it to cause any trip hazards and in the last two years without the cones, I have had no hazards yet.