LoTR is driven by people not wanting a tyranical force of evil to win and enslave/murder all the good guys. The only backstory that matters in the slightest is Aragorns
I think this is a very weak reading of LotR.
Start with Frodo and Sam (who are probably the two most inter-twined characters in the story):
* Frodo taught Sam his letters; Sam starts out on the adventure as Frodo's loyal sidekick; by the end of the adventure Sam has become an autonomous person able to pursue his own vision of personal and social good (everything from defeating Shelob, to carrying the ring, to replanting the party tree, to becoming Mayor of the Shire effectively for life);
* Frodo was "meant to have" the ring, because he inherited it from Bilbo, who was meant to find it; Frodo suffers as a result of his burden, literally as a ring-bearer, and in various other ways (Morgul blade, Shelob's sting, betrayal of and by Gollum, etc);
* Frodo is Bilbo's heir in other ways too: he wears the mithril coat, which establishes his affinity with dwarves; he can speak and read in Elvish, which establishes his affinity with elves (we first see this when he meets Gildor and friends in the Shire, but it is reiterated throughout Books 1, 2 and 3); he is master of Bag End, which provides a focal point both for the opening of the adventure (when Gandalf tells him the story of the ring) and its conclusion (when the Shire is scoured).
There's no doubt more that could be said, but those are some of the obvious ways in which Frodo and Sam's backstory matters to the story. And the story is obviously far more powerful and evocative as a work of romantic fantasy (or "fairy tale", to use JRRT's nomenclature) because it is
Gollum who proves to be the vehicle of Frodo's redemption, and
Sam (
not an elf-lord) who rescues Frodo from Shelob and Cirith Ungol, and
the Shire (not, say, Bree) that has to be saved from Saruman's final work of "mischief in a mean way", etc.
The same sort of account could obviously be given for Aragorn and Gandalf (the other two main characters). Pippin, Merry, Boromir, Faramir and Eowyn also have meaningful backstories the inform their place and actions in the story, but they are a little more secondary.
Gimli and Legolas are probably more secondary still - there most straightforward contributios are to be
the dwarf and
the elf - but even then their backstories are hardly irrelevant, as begins to come out in the Moria sequence, comes out more fully in Lothlorien, and then plays out in the encounter with Eomer, at Helm's Deep, and when they take the Paths of the Dead with Aragorn. You can't just plug a dragonborn and a half-orc into the story and have it remain much the same.
You dont get a strong character or anything interesting from a couple paragraphs about back when you were a turnip farmer.
In that case, why would someone choose that as their PC's backstory?
Luke Skywalker is the son of a great pilot and Jedi killed by the evil wizard henchman of the evil emperor.
Han Solo owns the fastest ship in the galaxy that he won in a dubious bet.
Ged is known to be a powerful wizard in waiting, if memory serves correctly given his true name by Ogion, the most powerful wizard on Gont. As a boy he conjures up a mist to defeat the invaders of his village, and he goes on to be the strongest pupil in his wizard shcool.
Stephen Strange was a great surgeon who lost the use of his hands and travelled to the "mysterious east" in search of a cure, where he learned wisdom and the magic of the Ancient One.
In my first Rolemaster campaign, Franklin of Five Oaks spent his youth hanging out with the trader (name now forgotten, but I think it's in the City of GH boxed set) and checking out the trinkets while being trained by a mystic who lived in a great hollow tree outside the village, living as a hermit lest his enemies track him down.
In the Burning Wheel game I GM, the wizard Jobe's brother was possessed by a balrog, and Jobe's ambition was to free him from possession. (In play, it ended up that the brother was killed by another PC, who had studied under the possessed brother and been mistreated, even tortured, by him, and was finally able to get her revenge.)
In my current Classic Traveller campaign, Vincenzo von Hallucida won his yacht by cheating at cards (service: noble; DEX: 12; skills: not much, but includes Gambling; mustering out: one roll, giving him an interstellar yacht) - and was hospitalised by the resulting beating that he took (near-miss survival check leading to forced mustering out). That was why the (renegade?) Marine Lt Li needed to approach him for he mission - because her original crew had lost their ship! How to make contact? Well, a former shipmate of hers was working in the hospital where Vincenzo was being treated (another PC, with service in the Imperial Navy and whose skills included Medic-1).
From the initial PC gen, starting world gen and random patron gen in that Traveller game we've got a whole campaign.