Can the people asking for an Apple TV SDK explain the need for it? I've never understood the request. With mirroring on all iOS and OS X devices doesn't that pretty much mean you can do anything on the Apple TV anyway? Why bother adding in an SDK for the Apple TV when there are already SDKs for iOS and OS X?
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Why bother adding apps on it at all? Just one more thing to track and manage on Apple's side, and right now you can run anyway app on your ATV anyway with mirroring. So I can't see why it's worth the effort. Might you explain a little more?
Mirroring doesn't work well for games. Also, streaming/mirroring is one extra step for the consumer and Apple likes to keep things simple.