As someone who loves his iPad, this makes me sad. It’s not enough for me to abandon it but it’ll definitely make the upgrade decision tougher when the time comes.
Does iPad even support Xbox1/PS4/steam controllers? Last time I checked, at least PS4 gamepads did not work on ios. Without those (certainly Xbox and PS4 ones), I’m not sure I’d want to stream games onto an iPad anyway (not that this makes it better, if anything it makes it worse).
I guess the problem is the store. The app allows to access valve's store (which is far cheaper than games in the apple store). If they remove the ability to buy games I am sure the remote desktop app would be ok.
The difference is in the steam store app doesn't actually enable you to play the games on the phone itself, while the steam link app will let you do exactly that.
If they were wrapped up in a single package that was marketed towards buying and playing those games, using the same logic they quite probably would be.