Dragonriding with old mounts

Why is dragonriding only available with the four new mounts, 2 of which are absolutely hideous? Blizzard please allow us to use dragonriding on our other dragon mounts as well. I would love to be able to bring my old dragon friends along to the dragon isles. The Obsidian Worldbreaker and the warrior class hall proto-drakes for example.

That would be somewhat impractical. I could see doing this maybe for the older dragon mounts but it doesnt make sense with a lot of flying mounts such as the flying horses, magic carpets, kites, etc. I think it would be neat if they did allow more dragonriding mounts but i dont see Blizz devoting the required resources to make that happen.

Blizz will more likely allow the dragonriding mounts to fly ‘normally’ outside the dragon isles.