In tabletop RPGs, we have a clear Revealed Preference for what this medium is- what the playable space allows.
This preference is for a gameplay paradigm where the players comprise a team of complimentary experts that cooperate in working to fulfill a set of strategic objectives despite limited resources and incomplete or unreliable intelligence. All conflict and reward is external; due to players being direct participants, with virtual skin in the game, workplace thinking common in real-world examples of such environments (military, rescue services, etc.) takes hold and thus punishes antisocial behavior. In short, mercenaries and professional team sport atheletes.
D&D established this dominance, and due to the Network Effect it is more difficult than most to get away from that context, but I want you to consider another reason for why this paradigm comprises the playable space for tabletop RPGs: It's What a Game Looks & Feels Like.
In short, that is the space because a normie seeing it in action (with maps and minatures) clearly sees an obvious game being played here. There are clear objectives (e.g. get the treasure), ways to deal with obstacles and opposition (spells, items, abilities), and a clear eusocial element (teamwork required) that is necessary for success.
There are few deviations from this paradigm because they don't have this emergent phenomenon working for it. Call of Cthulhu works due to its Cosmic Horror source material, but not really in any other context. Horror gaming otherwise, if it is to be viable, always becomes Team-Focused Survival Horror/Monster Hunting, in which case you get Chill and at that point you might as well just use D&D and add guns and explosives.
With Traveller, you get the difference of adding what is usually considered endgame play (logistics) right away and that has the effect of driving player decisions in what they want to do- and thus contributes to the pattern of campaigns skewing towards Mercenary Company or Free Trader Speculation paradigms because that endgame focus pushes players one or the other reliably. It gets a lot of grips, but this phenomenon also contributes towards the game's longevity as a commercially-viable alternative to D&D.
Pendragon is meant to subvert this by design, and when the players sign on it has the desired effect. The problem is that most players aren't going to sign on because this game doesn't do what they want, and that's why this game is a respectable--but rarely played--gem of a classic.
The World of Darkness games always turn into Superheroes That Gossip Like Teenagers because most players reject the assumptions of the setting. Why? Because there's no game there, so they go with what they know and make the game happen where they expect it to be; everything published since 1991 has been some form of reaction to this emergent behavior.
And as for Superhero gaming? The problem is always the rejection of bullshit genre tropes because those tropes exist for stupid reasons; actual play consistently reveals players to be sufficiently pragmatic as to permanently put down predatory threats- they kill villains. Reinforcing this preference? It's always better for morale, for the territory served, etc. to kill the villain than to let it live; you have to go out of your way to make it worthwhile to not do this, and superhero games/campaigns that do so never have the success that those what let the opposition get obliterated for good do. Lensman morality prevails because it works.
And, when broken down, all of those paradigms ultimately come down to that of D&D applied to a non-fantasy context.
There is it, folks. We have the answer: this is what the medium allows, and those who want it will not brook anything else.
Which is why those sincerely wanting something else need to stop looking at RPGs and go elsewhere- and those who are satisfied need to help push those folks to those alternatives, where they belong, so they can stop fucking up the tabletop RPG field for the audience already well-served by what already exists. Go make your own medium.