Stadia feeling more and more like a data collection exercise than a legit service with long-term sustainability or even intent.
I mean, that is Google's traditional business model -- create services that can easily collect user data and sell that data to third parties. I'm guessing its various partners in Stadia, like Ubisoft, are interested in seeing demand data for this type of game delivery model, and Google's more than glad to put up the facade and shut it down later if the data shows we don't want it. Narrowing it down to just Pixel, or WiFi, etc removes a lot of variables, and it'll allow better data and usage tracking metrics once the variables open up, and I think they'll open up very gradually so that there can be a more comprehensive analysis done to make guesses as to how big each variable impacts market demand and satisfaction with the service. Run it on the most Google-controlled set of devices possible at first, then see if by opening it to, say, iOS if demand makes any difference, etc...
I feel like Stadia is a lot less the swinging "future of games" promise that its reveal was trying to go for and more like a pop-up store experience that's back end is just exchanging the data collected with partners like Ubisoft so they can start seeing if its viable to plan their own infrastructures and delivery systems. Unlike Google's other stuff, there's cost associated with getting in, though -- have to buy your games and have to have reasonably good internet.
