TBW also lets the ECU programmer change the relationship between the twist grip and the throttle plate. 10% on the grip might be 5% at the plate if they're trying to smooth out off idle power. This lets the engine designer give you nice linear power very easily, without making as many compromises in engine tuning that reduce power. On some newer car ECUs there's a sophisiticated map for the relationship between the throttle pedal sensor and the throttle body plate. If you have the right tuning software you can modify this yourself. That's a lot easier than going into the machine shop and making a new throttle cam.
In the cases where the owner has the ability to access the tuning, electronic controls are far superior to old mechanical ones when it comes to home tuing. I'd rather adjust the ECU with a laptop than replace jets, slides and needles in a rack of carbs.