Why isn't Roku on the List Of TV Providers on so many TV Networks Websites? Roku is MY TV Provi

This reply mentions using Justwatch to find platforms for particular movies or shows. Yep, justwatch is a great service but it is even handier to use as an app on a TV.  Other providers like AmazonFire, Apple, and Samsung make it possible to use the app. When will Roku make it available? Switching between a phone and a TV is not always convenient, especially if more than one person is watching.