We don’t? This isn’t a complaint I’ve run into before. I’ve always found it useful and descriptive, and appropriate for a slightly more formal register than when I’d just use “gay,” or even just for some variety’s sake. It also works well with the terms “heterosexual,” “bisexual,” “asexual,” “pansexual,” “demisexual,” and the like.
Tons of people have already said a bunch of wonderful stuff on this topic (as well they should, considering how many replies there are between this and me writing now). To add on:
Certainly it will depend on the story. Let’s start by considering those stories which reflect real life. In some settings, certainly their are more people of some identities than others. However, this is often used as an excuse to focus solely on the more commonplace story. Take gender for example… we really ought to see an equal balance of male-dominated and female-dominated stories (alongside plenty of more evenly balanced ones!), but it’s the former that exist in predominance. An individual story taken in and of itself does not become bad just because of what cross section of identities it has or doesn’t have. Taken as a whole, however, it’s pretty blatantly obvious that certain types of people far and away dominate storytelling.
People say “why should I make the choice to include minorities…” but every time you include majorities that is just as much of a choice. If someone needs a reason to write, say, a cast full of Deaf Latino trans men and lesbian intersex biracial people with schizophrenia who are also left-handed and have gluten allergies (and are vampires, why not?), then it is just as much the case that you need a reason to write able-bodied neurotypical cisgender white heterosexual men. Sometimes that reason can be as simple as “these people exist in reality.” But if your only reason is “these people exist in reality” and they all keep turning out the majority way, then it ceases to be a representation of reality. If your reason is “I’m writing about a segregated institution,” then sure, there are plenty of those that are interesting to write about… but if all the segregated institutions being written about are for the majority, that too is neglecting a vast swath of human experience.
If you’re writing something nonrealistic, then you pretty much get to make up the rules. But, while I have no objection to fantasy medieval Europe as a setting in and of itself (I’ve certainly used it), I do have an objection when fantasy as a whole represents that and neglects all the other possible fantasy counterparts (not to mention the rewarding task of fantasy settings that correspond directly to no specific Earth culture).
As for the topic of “cis.” While I certainly agree with the point that it’s, well, not nice to call someone something they’ve specifically said not to call them, I really do wish to throw my voice in with those who consider it useful.
(I realized this ended up a bit TLDR. Just in case, I’m quoting my conclusion up here:"my main point is that, if you object to the word “cis” but are fine with “trans,” that’s a double standard. )
I’d like to draw an analogy with the term “heterosexual.” So the term “homosexual” came first, and at that point psychologists were pretty much just talking about “homosexuals and… you know, normal non-deviant people.” (Well, when they weren’t calling us “Inverts” or the like.)
So, wasn’t it nice when they came up with a term to refer to heterosexual people as well? They took an exact analogy, even, where “homo” means “same,” and “hetero” means “different.” This didn’t serve to insult heterosexual people (I mean, it was mostly heterosexual people using these terms). To the contrary, it normalized sexual orientation, rather than the terminology simply marking the “other.” (And then other terms came later, as additional important improvements.)
(It’s also a darned lot better than the term “straight,” which implies correctness and normality, but that would appear to be a losing battle.)
"Transgender and “cisgender” are direct analogues of the above. It even follows the model of using the same prefix system. (“Trans” meaning “across” and “cis” meaning “same side of.”) So again, instead of just marking trans people as the “other,” it’s making it so that we have words for multiple sides. (Really, it’s just like the Romans having a Cisalpine Gaul and a Transalpine Gaul. Gaul on Rome’s side of the Alps; Gaul on the other side. Gender on the designated-at-birth concept; gender across from the designated-at-birth concept.)
Or take “Deaf” and “hearing.” Am I going to feel like my identity’s being boxed in as a hearing person because I’m being labeled for my non-deafness? It’s just a useful way to talk about people who aren’t deaf without saying “people who aren’t deaf” all the time.
Also, it’s just a whole lot easier for people in the advantaged group not to have to think of themselves as a member of that advantaged group. When you’re part of a disadvantaged group, you don’t have that luxury; life is going to remind you. As a homosexual person, although I get a say in whether or not I want that term applied to me, it still ends up being a part of life that it is simply impossible to be unaware of. As a cis person*, however, in the course of my regular life I can usually ignore it. It really only comes up when I choose to think about it or people talk about it or I just hear one of these words. So terms like “cisgender” or “heterosexual” or even “hearing” end up being a way to describe those identities at the same level that society normally describes transgender, [insert lots of options]sexual and Deaf people. It’s a way of acknowledging that to identify one’s gender with the sex assigned at birth, to feel sexual attraction to the opposite one, to be able to hear, etc., are just as much “things” as the alternatives are.
I mean, I can agree with not liking to see identities used as insults, like what people were describing with cis-het***. (I can say as a general rule that I dislike insults.) But I do think this terminology provides useful words which directly describe majorities using the same level of language that is apparently normal for minorities. (Cis-het might be different. I’ve never seen someone called trans-het or trans-homo. It still doesn’t carry the same weight as insults that have the prejudice of society backing them up, though.)
So really my main point is that, if you object to the word “cis” but are fine with “trans,” that’s a double standard.
(If I want to be super-pedantic, I probably feel more cis-ish than fully cis. But cis enough to be advantaged. Naturally, if anyone else doesn’t really feel cis, then don’t call them cis if they don’t want to be. I’m not in the business of invalidating anyone here*)
**(Is that a business? Could I make money? "I charge $100 an hour to invalidate identities. First call of business; claiming that people are incorrect in identifying as human but are actually hot air balloons.)
***(Could I identify as cishomo? I shall pronounce it “sea-show-moe” and be disappointed if I don’t see someone named Moe emerging from the waves.)
For those who just don’t like the sound of “cis”… on a pleasanter note, the Classical Latin pronunciation would’ve been much like the English word “kiss.” Sounds nice to me 