In fact, I would argue that the whole point was that it wasn't prominent. It was, in fact, a niche within a niche within a niche, hard to design for, hard to exploit as a product (the other agendas welcome creator-made elaborations in a way Story Now does not), certainly not easy to get into the headspace so you can do it, etc. But it was something a niche audience wanted, which wasn't being served.
It makes me think of horizontal market segmentation, Dr. Howard Moskowitz, and the "a large group of people really wanted Extra Chunky but literally did not know it" thing. GNS was a tool for drawing out, naming, and explaining a desire that had gone unserved, and in so doing, prompting the kind of thinking and preparation that would prepare someone to serve that desire. It was a product of its time, and it shows, as I've said earlier. I think it was heavily shaped by the fact that Gamism dominated the TTRPG market (and still does), while Simulation looms large in the public consciousness even if it isn't necessarily well-served in the dominant games.
I will not call my four-part approach a "Fourfold" model, because I do not take seriously the idea that my four purposes--more or less formal causes, in the Aristotelian sense--are the only ones. But I have laid it out the way I have because I see patterns, symmetries between the four purposes that actually do reveal something, not merely label things. Every "game-purpose" I've proposed has a driving concept (the first part of the pair) and an action-space (the second part). Score is the driving concept of "Gamist" play, the idea that performance can be evaluated and ranked in some semi-objective way, and Achievement is its action-space, where one attempts tasks that are worth doing in the hope of proving one's skill. (As noted before, the reason why someone might attempt this could be "prestige," but I consider that a final cause, not a formal one.) Conceit is the driving concept of "emulation" play, the desire to explore an idea or a theme to see the tone and/or results it produces, and Emulation is the action-space where that idea is examined and displayed. "Groundedness" is (what I consider) the driving concept of "simulation" play, the idea that the play-experience should be fully rooted in rational explanations and naturalistic causal relations, free from (so-called) artificial manipulations; "Simulation" is the action-space where that commitment can play out, the metaphorical turning of the crank, the "rules as physics engine" idea. "Values" are the driving concept of "Story Now" play, the idea that the players themselves choose what things are worthy of pursuit or dedication; "Issues" are the action-space, where those (player-defined) values become subject to conflict, and the resolution thereof.