[IanJRedman]

Not having to pay fees to Apple and Google would also be another benefit of their own hardware.

IIRC News Corp had investments in Roku, so that was why they made all of the NOW TV devices. Similarly, Comcast has been pursuing their own line of IP based streaming devices (as they need to get away from traditional cable TV to free up capacity on their US networks) and it seems that's where Sky Glass/Stream originate from.

Yes, apparently Entertainment OS (the operating system on Sky Glass and Stream) is basically the same underlying OS used on some of Comcast's kit in the US. In fact, the Sky Stream puck appears to be closely modelled on Comcast's XiOne:

corporate.comcast.com