True 512 patches are a lot for playing. Still it can be problematic for backing needs like midifile / style revoicing. This needs a more static yet extensive sound base. One aspect here is again the library idea and additionally that you are not on an island doing all by yourself but share backings or registrations with others. Maybe professionals or genuine bands don't want this which is understandable - but in the world of just playng for fun and covering songs sharing stuff is an invaluable time saver.
Well, isn't software far more likely to achieve to achieve shared accuracy than a scenario which, presumably, means everyone has to own the same expensive hardware modules?