Lots of Smart TV’s have a terrible OS, just look at Samsung. Fantastic displays, horrible UI, lots of apps missing.
Another benefit of Apple TV is unified search across your apps. I open the TV app on my Apple TV and can search for the movie or show I want and it takes me directly to the right streaming service.
“I want to watch Apple TV+ on my Apple TV app on my Apple TV 4K” has quite the ring to it, not confusing at all /s