As someone who worked for a video streaming company with lots of clients and currently works for an audio streaming company with lots of device support, I thought I'd just drop in my 2 cents:
Tizen, WebOS, Vizio, Comcast X1, etc all use what we refer to as 'Web TV' which is vastly different than 'Web Desktop' which is what you use on a computer. There's also 'Web Mobile' too, which usually is a subset of desktop with a skin change and optimizations for touch instead of clicking, vs remote w/ TV.
Writing Web TV apps for video is super super annoying. Why? Because the standard web javascript frameworks (think React, Vue, etc) are traditionally too slow to work on 'low powered tvs'.
There's pretty much 4 type of clients for TVs:
tvOS-based ones, which can share code w/ iOS
Android-based ones, which can share code between TV and mobile
Roku, which uses a thing called Brightscript and is pretty awful
And Web-based ones, which have its own unique flavor. If you used channels, you know their current WebUI is not designed to be a '10 ft interface' it's a barebones admin page. Clearly fancy/pretty web frontends aren't their forte.
Say they were to make one. Then you run into TONS of playback issues. For example, ATSC or OTA tv in America (and DVB-S too, IIRC) is all mpeg2 and ac3, neither of which a browser supports. They'd have to then have the server transcode both the audio and video, which adds tons of overhead to the experience, never mind ATSC 3.0 using hevc and ac4, also things that many browsers do not support, forcing a transcode for playback.
The experience on web TV platforms when you dont control the media 100% is hard. If you ever used Live TV w/ Plex on a Web TV platform, you'll see what I mean and thats with a vastly larger dev team.
And also the variations between the TVs is horrendous. Take just WebOS: My 2022, 2021 and 2019 WebOS TVs all run different versions of WebOS, meaning different chrome versions and different experiences since there's no incentive to continue to update appliances like this.
In my own apps I've supported I've submitted countless numbers of weird edge cases that vary across platforms and one of our QA labs had over 20 tvs for testing once, because a bunch of them (Roku, I'm looking at you) don't create dev kits and allow vendors to literally fork the platform, so we were forced to build two walls of TVs. Such a mess. Roku's playback is a black box that you throw packets in and hope the thing you want comes out.. did I say hope? I meant pray.
Android and tvOS are the easiest to write something as complex as Channels where the devs have the most control and have the ability to use lower level of programming if necessary, and not be stuck w/ the stock video players (exoplayer and avplayer, respectively) if they want.
Let's have them focus on 2 great clients, instead of 3-5 half baked ones.