2ENGOP I also asked this question when I was doing a perf eng course (737ng) at Boeing. They said it was requested by most of the airlines? long time past - That LRC FMC should produce the same data as the aircraft perf manuals available to the pilots on the flightdeck? (no wind) as mentioned. What Mutt said.
But as to its usfulness as a function in everyday life without wind data, I dont know. But its why you find most Airlines (that I know anyway 73) use a standard CI which gives a good speed Vs fuel burn and ECON will ajust speed for wind which is what you want. Some will produce a CI for every flightplan. Irispective you will go further using LRC with wind data, Im not sure I agree its the most efficent way to fly as you tech book says - too many variables. Hence proper CIs and ECON.
Anyone care to add, correct?
Rgds