Roku is a privately held company free to run their business any way they want. I suspect this change is for legal and channel quality control reasons.
DishWorld is probably in a much better position to assure that developers have licensing to use their content and provide reliable, quality streams and customer service.
That's my take anyway.
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No, I don't work for Roku.
Netflix Player N1000X, XDS 2100X (premature death by lightning)
Roku2 XD 3050X, Roku2 XS 3100R, Roku2 4210R