Gas engine-powered airplanes tend to be heavier and costlier than glow-powered aircraft, so it makes sense to build some reliability and redundancy into flight-critical (and also safety- ) systems. And opto-isolated kill switches make good sense, too: it is good practice to put the RFI-producing ignition components up front and the RFI-sensitive radio components to the rear, distance is the key here.

My 2c...

--Bill