What if you had a device that was just cable/sat favs. You would need to link to the cable/sat device.
What if you had a device that was just surround modes of a receiver. You would need to link to the receiver.
What if you had a device that was all the am/fm tuner commands for a certain model receiver. You would need to link to the receiver.

There's a lot of examples where it would be useful. The thing to remember is that if you are going to export a device, make sure there are no shortcuts/macros (AV receiver volume, tv aspect mode), unless they are intended, as in the above examples.