"launch" implies they have to do work. I think from the youtube link further up the thread the reality is all they have to do is remove the bit that "blocks" the app from working on the chromecast.
I'd suspect the answer is a mix of
a) google wont give us money, sony did so they get an exclusive
b) if we enable it we have to support it / QA test it and at present its not a big enough market / user base - maybe if the device become smore popular
I think both are short sighted personally, the new chromcast is a great little device and i find myself watching shows on it far more than i do on my roku box. Even though the apps i use ( disney/netflix) are on both. That means i dont see the now tv app on my screen so much and I'm using it far less. In time if i stop using it then i may start to question its value.
To me this sums up the difference in attitude between the new media companies and the old. The new companies want as many people as possible to use their service; and do everything they can to get their app out there. The old act like they are doing us a favour by letting us consume their service. The app is written, but Sky is not willing to let us use it unless Google pays for the privilage.
This is why I only pay for Now TV when I have to (I watch F1 so just subscribe to the season in the cheapest way possible). Whereas the new media companies I am happy to subscribe to all the time. If Sky treated customers better then I might use their service more.
What's more annoying is that it's launched finally even on Firestick devices, so it's already running on yet another Android based device. Hopefully they realise how easy it will be to launch on Google Tv, and add it soon. But given how long it's taken for the likes of the Firestick and Apple TV to gain anything worthwhile I wouldn't hold my hopes up.
One thing that we have to bare in mind is that Sky being owned by Comcast, things will be moving along quicker than what they had been before.
Since under the helms of Comcast they have introduced 1080p with 5.1, offline downloads. Launching on Sony Bravia Android TVs with more devices on the horizon.
Hopefully we will continue to see Now TV evolve into a better service in this new new year.