I don't know that this is actually true of all morale systems (for instance), nor that the same statement couldn't be made about punching people or punching walls. But in a "simulationist" game, for better or worse we're committed to handing at least some of this to the system to determine.
Just one example:
Rolemaster, and similar systems, pay a lot of attention to the passage of in-game time: spell casting times, ritual times, healing times, travel times, times to manufacture things (typically magic items but sometimes weapon and armour also).
In these systems, it also typically makes a big difference if someone is ambushed armed and armoured or unequipped, or (in the case of a spell-user) at the start of the day when they're full of spell points or at the end of the day when they have few or none left.
So the players pay a lot of attention to these things, build plans around them, etc.
But if the occurrence and timing of events like ambushes (ordinary ones, or scry-teleport-fry ones), visits from important people, presence of possible contacts in the market, etc is all just decided by the GM (because there is no system to support this) then the players' planning and decision-making around the parameters of time, place etc may become largely illusory.
This creates pressure, on the GM, to make decisions about these events in ways that will honour the players' decisions and planning - but that sort of approach to GMing directly undercuts the "simulationist" ethos, and there's also a real question as to what it means to honour decisions and planning in a context where its relevance/success depends so heavily on GM decision-making.
As I posted upthread, for me this is not an abstract concern. It's the hard-earned lessons of GMing 1000s of hours of Rolemaster.