I won't pretend to give you a generalized answer, but rather answer it for myself and my household:
(Context: I work at Netflix, which may make a difference so it's worth noting. That said, I'm back-end cloud systems, with nothing to do with consumer devices).
I consume my media from several sources, including iTunes, Hulu, Netflix, HBO Go.
I could get a SmartTV that lets me access them, but IME, smart TV manufacturers move pretty slowly; I also think of my TV as just a large display, and imbuing it with more smarts makes it more painful and expensive to upgrade to something else. By focusing on modularity -- this TV is just a bunch of HDMI ports with a big screen -- it lets me optimize the TV for display, and use another device for content access.
Which is why I prefer the AppleTV rather than a SmartTV.
(We could have another conversation about AppleTV vs Roku or the Fire TV, but that's outside the scope of this particular comment thread).