Maybe that's exactly the point - they're consumer OSes. And while Android already does this, with intents, I doubt most consumers are very happy with this feature (if they even know it exists).

You want to do something with an image, for example, and you're greeted with a huge list of apps that all claim to handle images. Not only is it hard to find the app you want, most of the ones in the list have nothing to do with the task you're trying to accomplish. Hardly user friendly behavior.

FWIW, I personally don't really mind the huge list and can find my way around it, but I'm a heavy Unix user that does most of his work in the terminal already. Most consumers are not.