It's one thing when racing engines have stupid, flat advance curves because someone hasn't been able to find a suitable programmable ignition; it's another when most street bike engines still have, in general, no more than two dimensions to their spark control map, and don't alter ignition advance with respect to load. Generally, because cylinder-filling is low during part-throttle operation, engines like, run best, and give best fuel economy with more spark advance then than they'll tolerate with full throttle.
The only motorcycles that usually offer such sophistication are those that are fuel-injected, and have a single black-box controlling both injection and ignition. Things like Ducati 851s offer marvelous thottle response and drivability, and I've often wondered how much of that was due to the right ignition advance as well as the right mixture. In any case, the best-running Big-Twin Harley I've ever ridden was one fitted with Accel's aftermarket fuel-injection -- a system which, surprise, maps ignition advance at least as accurately as its injection, and gets appreciably better fuel-economy than the stock Harley carburetor.