There are sometimes issues you can't explore directly because they're largely taboo and editors or viewers will say no. In the 1992
Star Trek: The Next Generation episode "
The Outcast," Riker falls in love with a J'naii person. The J'naii considered any gender expression to be aberrant and sexual congress between male and females to be both yucky and unnatural. Soren identifies as a female, falls in love with Riker, but when they try to escape together she is captured and forced to undergo conversion therapy to return to their genderless standards as nature intended. Even at the time, it was pretty obvious this was a ham-fisted story about gay people. So why not just use gay humans? Because at the time, the networks that carried the syndicated TNG would have balked and they would have faced backlash. Making the J'naii androgynous provided the producers with a plausible deniability if someone complained they made a pro-gay episode.
Likewise let's take a look at "Let That Be Your Last Battlefield" from the original series in 1969. It's all about a species of black & white aliens who dislike one another because of their phenotype. The two men in the photo below hate one another so much that they continue their fight even after learning that their species fought itself to extinction. Any idea what message the writers were trying to send to their audience in 1969? It rhymes with glacial harmony. CBS would not have aired the episode if it was overtly about racial harmony between blacks and whites in the United States.
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On the other hand, neither one of those episodes is particularly good. But writers can still use lineages, species, race, or whatever we're calling them now for plausible deniability. They can include write about strongly authoritative elves conquering territory and forcing all non-elfs out to tell a story about fascism without having to implicate any real life group. And if someone complains that the writers should keep politics out of the game they can just say, "Hey, it's fantasy and we're just talking about elves. We didn't say anything about fascism."