Not much to say beyond our experiences differ.
Sure, except my experience shows that it is entirely possible. And I don't think that I or my players are exceptional in some way. So I wonder what makes that the case for you.
By gaming, I mean making a series of meaningful choices in the context of the game world. E.g., I choose to do X or Y. By storytelling, I mean developing information about the world. E.g., deciding my character grew up in a barbarian clan.
Chess is a game; only gameplay decisions are made. Unless you want to like, decide that you're playing as France and England in the hundred years war or something.
Chess is an interesting example. Two sides, equal in all ways, with total and complete view of the board. Nothing is hidden from either side. And the game still functions.
Because in my mind, the NPC with the trait that I'm unaware of as a player creates ambiguity about my available moves that doesn't exist in chess. In chess, I always know exactly what move I can make, and where it leaves my piece in relation to other pieces. There's no surprise because of some unknown element.
So, I think the chess comparison actually does more to support my comments.
Narrative games have much more storytelling. There are rules for adjudication so you aren't just making things up, but the players have much more control over the content of the fiction.
So it's less storytelling if the GM authors the content?
I don't think the amount of "storytelling" as you call it is different from game to game. I just think that in one example, the GM is responsible for the lion's share, and in the other, it's spread out among the participants more.
Just an extreme example to show the point--NPCs having strong desires is not a railroad.
They can certainly contribute to it. Which is why the GM should always be considering such things.
The example is not well defined enough at the moment. Is it a religious tenet that fleshes out the world? Does it relate to the characters backstory? Is it demanded by his order?
Yes, this is why I said that IF the reason is solely, or even primarily, "because this is how the GM imagined it" then that's not a good answer.
If there is a compelling reason, then so be it. Also, and most importantly, if it's known to the players. That's the key. It's what makes the chessboard clearer, to lean on your analogy once more.
My point is that these are things the GM should consider. So many folks in this thread and others are advocating for a specific style of play, and then not showing any kind of consideration for how their choices as GM may impact that style of play.
If sandbox play is about player driven play... about letting the players direct what play is about... then a GM needs to be considering this at all times when he's preparing. Even a trait of an NPC. Maybe he likes the idea of the priest who won't drink... okay cool, that maybe makes an interesting character. But that's not the sole consideration he should have. He needs to consider how that NPC and his traits may impact play.
Interesting, because this is the complete opposite of what I see these kind of fixed things creating. If lots of aspects of the world are subject to the players creative control, and they can do this while the game is in motion, then the activity is more group storytelling. Its not the GMs novel; but it is the gaming groups'.
In contrast, if things are fixed, then gameplay becomes more possible. The rook moves like so, and this gives the players certain choices they can make. The priest doesn't drink, and that gives us choices about how to approach them.
I want play that is collaborative. I don't want to script a bunch of NPCs ahead of play as lonely fun and then watch as my players slowly suss out all their traits just so that they then know how they need to interact with them. I want to get to more interesting stuff... so I'm going to communicate to my players what they need to know about an NPC when I introduce them. There's no need to be coy about this stuff.
I don't know what your experience is with games you're labeling "narrative", but your description of them seems off.