There has been some useful downsizing. Batteries have gotten smaller. Advanced magnet technology has reduced the size of some starter motors and alternators. Ignition coils can now sit inside the cylinder head. But getting everything in place, keeping weight and weight distribution under control, giving parts the necessary clearances and making sure that sensitive ones are protected from heat and vibration...that's a challenge. It's not like a car, where you can find unused space under the hood, in the trunk and maybe in the wheel wells. With a motorcycle, if you don't create the needed space in the original design, you're unlikely to find it later.