It isn't even that. Each machine has it's own user interface quirks that arguably change the outcome of the piece you're working on. The classic example of th

It isn't even that. Each machine has it's own user interface quirks that arguably change the outcome of the piece you're working on. The classic example of this is the 303 which was originally designed as a 'robot' bass-guitar companion for a guitarist, but because of its user-interface and the way it could be pushed to extremes, you get acid-house and techno. There's also the latency issue of controlling anything via MIDI, a tweak of a filter will have a slight delay, and that can be enough to throw you out of the creative space you'd otherwise be in.