Morale checks -- or reaction rolls -- can be a useful tool as GM if I have no particular reason to choose when the goblins will break and run or whether they will be immediately hostile. Since I personally like a little chaos at the table because I too like to be surprised, I tend to incorporate random stuff fairly regularly, including how monsters and NPCs react and behave.I largely agree, but then I even more dislike the asymmetry that arises when there's Morale checks that can force NPCs to flee etc. Same applies to "social mechanics" e.g. Intimidate in 3e D&D.
What's the answer? For me it's to drop or ignore a lot of those sort of rules completely, as the other option would be to have them apply equally to PCs and NPCs alike, and that would play hell with player agency.
But I think the literal most important part of RPGs is player agency over their own character's choices*, so I don't like mechanics that remove that. I don't mind things like intimidate that apply a condition against the PC, but it is up to the player to interpret how the fiction and mechanics combined effect their roleplay.
*Let's NOT use this thread to argue about the definition of agency, please.