Activision-Blizzard-King isn’t a dominant company in any segment. You can’t say the same for steam. Regulators would have a much easier time blocking such an acquisition.
So long games don’t force it to be on, then whatever. Although I expect it to become a requirement for a usable framerate for next gen games. Big developers don’t want to optimize anymore and upscaling/framegen technologies are a great crutch.