I prefer it primarily because it "just works". I don't use my TV often these days, so I stopped maintaining all my custom hardware (e.g., Retro Pie). I've found that my Chromecast can be finicky; sometimes it doesn't like to stay connected to Wi-Fi--and it has no excuse, seeing how I'm using Google Wifi.

That being said, I do like the UI. I don't mess with it much, though; I mostly just talk to it. It does a fairly good job of figuring out what show I'm telling it to play. It works, it updates on its own, it doesn't brick itself, it doesn't disconnect from the network (because it's wired in), it's reasonably secure, it plays what I tell it to play. Good enough for me.

Depending on your use case, you might want to give Kodi a try if you're not satisfied with the mainstream alternatives. I haven't used it in ages, but I hear it works quite well these days.