Also: I write and arrange music for both acoustic and electronic instruments. Suppose I have some music that is currently rendered for a mixture of acoustic and electronic instruments, and I have an opportunity to take one of the lines that is electronically rendered at the moment and print it in a way that can be easily read by a human musician playing an acoustic instrument.
The one thing that I want, above all else, is for the part that I give this musician, printed on paper, will enable that musician to play the same pitches that my electronic rendering did, assuming of course that it is physically possible to do so.
I went back and dug up an example that is now ancient history–I wrote this 15 years ago! It is a computer-synthesized rendition of a traditional Irish tune.
Once I had it the way I wanted it, I generated parts for eight musicians: flute, violin, cello, 12-string guitar, harp, synth keyboard, bhodran, and triangle. As it happens, I knew in advance what instruments were available, and therefore what clefs, transpositions, etc. I had to use.
Now, suppose I have the opportunity to perform this music with a different collection of musicians playing different instruments. I want to be able to assign the various parts to those other instruments, with at least a starting point that has those instruments playing the same pitches as my original arrangement. I may then have to change parts of it so that the melodic lines will fit comfortably into those instruments’ ranges; but it is much easier to correct problems if one has an accurate indication of where those problems are!