There's a part of me that wonders if this wasn't by necessity.
I went into Best Buy just before Christmas and they had Google TVs and Amazon TVs everywhere, prominently displayed and fully stocked. They only had 2-3 little Roku TV's hidden in the back corner that I had to ask somebody to even find.
If I go into Sam's Club or Walmart, I can find Roku everywhere with great options.
It made me wonder if the other vendors were trying to push Roku out and because of that they were forced into a deal with Walmart to remain viable.
My solution has been a Raspberry Pi running Kodi.