So there is absolutely no requirement to have random movement just to go with premeasuring. If I remember correctly doesn't Epic also allow you to premeasure and have no random movement(how about Warmaster)? And neither does Warmachine/Hordes.
Now, whatever you need it or not I don't think is going to be determining of if GW would do it or not. Randomness seems to be the name of the game so I could see it being included for everything just for the sake of it.