Back when the GL1800 GoldWing was in development, Honda gave specs to Bridgestone and Dunlop to develop tires for it - sight unseen. This was told to us at a GoldWing rally by Dunlop engineers at a Q&A session. Now, Bridgestone and Dunlop have obtained test bikes since and developed several new tires for the GL1800 as well as Avon, Metzler, Continental and even (briefly) Shinko. If all of that development went into keeping GoldWingers happy, you would think that Kenda and others would "get with it".
You can't compare motorcycle tires with Spyder tires. Different altogether and economies of scale don't favor Spyder tires.