It have quite a big focus on assaults actually. Trying to kill dug-in infantry with shooting is almost impossible with most weapons (or at least very time consuming), if you want to inflict decisive casualties and seize objectives you are almost certainly going to have to assault (the exception is tank on tank armies, as they can't assault each other). Sure, if you catch an infantry platoon out in the open with artillery and heavy machine guns they are going to suffer badly, but in general you have to push forward and engage to get rid of infantry. It also features an actual effective pinning mechanism, something you need to employ as well as units you assault get to shoot at you but pinning them degrades their ability to shoot.
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.






