Problem is not about creating some type of sound live, but many kinds of sounds. If I was to perform material that is done with handful of pedals and shakerbox, certainly there is no need back it up with other things. But lets say if ones sound is build from other kind of sources what do not fit to suitcase. How to bring on stages such things as engines, piano, church organs, etc etc. Or to play with field recording from other ways than from backing tape or sampler. Same could be said about set that lasts 10 mins and is about one thing only. But if there is more.
I fully acknowledge necessity of aesthetic & theatrical value what Kollaps says. And I have admired for example some guys like Altar Of Flies actually playing with several meters long tape loops that run across the stage. But to bring actual tape loops on stage in my own case is utterly useless. If I was about to play sample of drilling sheet of metal, that's something what can be done actually live. If I was to play sample of recording of waves of lakes splashing against canoe, I know I will just have to do that. Can't "recreate" situation on stage. Then it's only choice whether you want to play material that can be done live, or material you'd wanted to, but can't. That's the moment of compromise I was talking about. Knowing that performing tracks "like they should", might become too much of relying on playback. This is of course reason why I personally tend to perform only "alternative versions" of released material, mixed together with things improvised on spot. And also in such cases, if size of suitcase is the limit, I can guarantee there is compromises toward studio situation.