It’s better used as an app on these devices. A webpage would be very cumbersome to use with a basic remote and lower powered processor. I also assume they integrated into search and other roku functionality.
1. Build an efficient "browser" (HTML5 runtime) that can run a web app.
2. Write a webapp specifically targeted towards TVs, includes 10 foot interface, etc.
Source: https://cobalt.dev/
https://www.theguardian.com/technology/appsblog/2013/aug/15/...