Why aren't Hbo or other networks available for android TVs with Comast Xfinity as a provider?

[AC Question]

I have a Sony Android TV. I also have a sucription to Comcast Xfinity as my cable provider. When i go to the Play store on my TV i can see all the network apps..ie: HBO, FX, ABC, ect. But when i try to activate my device, for most it says Comast is not supported. And unfortunatley comcast doesnt have an app for android TVs. So i cant get my HBO directly on my TV. Is there a list of apps available to Comast users? Or is this an issue with Android TV?