Originally Posted by
Mechalich
It's not really a holdover from Tolkien, but more an issue of scale and stakes and how they interact with human psychology. Human's mental systems are designed to apply to relatively small social groupings of no more than a few hundred people. Any event that involves more people than that struggles to scale effectively and becomes some nebulous 'really bad thing' unless it impacts you personally. This means that a framework based around 'we must stop Villain A from doing X horrible thing or 10,000 random people we've never met will die' has very little weight. Consider, for example, the effort to save the various people in the city at the end of Justice League (the movie), no one in the audience cares about those people and saving them is only relevant insofar as it reveals aspects of the characters in question.
And this generally holds as well even if the scale and stakes are upped to national scale - if the audience doesn't care about said nation, its potential obliteration may not resonate with the audience. For example, I'm a fan of the Aubrey/Maturin Napoleanic Wars novels, but characters in those have an ironclad belief that the English must triumph over Napolean and that their cause is absolutely just and righteous and while this is perfectly in character for people living at the time it still feels kind of strange to read. In a series that is set in a version of the real world, this can be a big problem.
By contrast, everyone lives on Earth, so blowing up Earth is guaranteed to matter to the entire audience. We can actually see the extension of this in space opera. Notably, in Star Wars: The Force Awakens are bunch of completely random planets get blown up and...no one in the audience cares because none of the characters are from those planets.
Now, Tolkien certainly represents an example of this in action. The Hobbits are from the Shire, which is about as far from the frontlines as it is physically possible to be. Therefore, in order to actively threaten the Shire, and thereby emotionally resonate with the leads, the conflict to come has to threaten everything. There's also the notable example in the Two Towers where Merry and Pippin, and by extension the audience, come to care about the despoiling of Fangorn Forest, and this is a good example of the quantity of words it takes to do this. 'Hijack a nuclear device and hold the world for ransom' - thanks Dr. Evil, is cliche, but it is instantly understandable.