There are certain guitar styles involving open strings that would be simply impossible to transpose without using a capo. They probably aren't used in jazz but in other musical styles they certainly are. I can think of a few songs that use droning open strings while fretting quite high up the guitar neck. These are impossible to play transposed without a capo regardless of technical ability. One song that comes to mind is Starship Trooper by Yes. You use whatever you need to use to accomplish the sound you need to create.