Ironically modern car CVT's use electronics to emulate a normal gearbox, because it feels better to customers. That way there's no advantage of having the engine rev at the most efficient speed while the CVT has quite a bit of mechanical drag. The NuVinci also has more mechanical drag than a regular IGH, but I guess the power/mechanical drag ratio of bikes is much better, but I don't think the difference between the efficiency of human cadences is a great as the revs of a car engine.