“Every customer should be greeted when they walk into the store.”

The singular “they” is traditional in English - it is very much proper English and has been around (iirc) since the 17th century. It’s only a big deal now because conservatives want to make gender a factor in elections.

"They" is the traditional English-language pronoun when an unknown person could be of either gender. "Mommy, my teacher said a funny thing at school today!" "Oh? What did they say?"

Teacher is singular, but assigning a gender would feel awkward if one doesn't know, so "they" is used instead.

Why not just pick new words to use?

Because the current word for it works just fine?

It's not though. Singular they goes back to middle English (14th century) it was just grammar Nazis in the 18th century that tried to stamp it out.

one always thinks of a plurality of people

Speak for yourself! I don't immediately think plural when "they" is used.

Person 1: Is your friend Bob coming over? Person 2: No, they can't make it, they're busy

One Bob, and we all know it's one Bob, no confusion. Look for context. It's not that hard.

One does not (always) do this. The singular "they" is many hundreds of years old.

If it confuses you, then I understand your confusion. Please read about the history of the singular "they" in order to resolve your confusion.

https://www.oed.com/discover/a-brief-history-of-singular-they

Why not choose new words? Languages evolve in a complex way. One reason is that "they" is an easy choice. Another reason is that many speakers react harshly to unfamiliar pronouns, therefore it promotes acceptance to use familiar pronouns in new ways. I wrote with the Spivak pronouns for years, but that led to more distraction than understanding, so when "they" emerged as a standard, I adopted it.

Really? I used they when I wasn't sure of gender (online games for example) before the pronoun use became common. I cannot remember anyone ever being confused.

Conservatives would probably get mad about that too so "they" works just fine

If you don’t know someone’s gender, what do you call them? Like, what if they present in a really ambiguous way? Or what if you’ve never even met them? Like say you’re about to sit down at a restaurant, and you notice a jacket on the seat, would you tell the hostess, “excuse me, I think the last person to sit here left their jacket.” Or would you just be unable to refer to them because you don’t know their gender?

Me talking at dinner: "Will you pass me the peas?" Cut to 5 people confused about whether I mean just one of them or if I want the whole table to all hand me the peas.

I get why they/them can be confusing because of the plural thing, but we are used to a quirky language. With a little practice, the tone and context clear up nearly all confusion. The rest is as easy or hard as what we have to do with an ambiguous "you."

PS Sorry to the "yous/yous guys" people. I am not trying to turn a blind eye to you obviously superior usage. It just really ruins my point.

Sadly, many educational institutions still teach a prescriptive form of English that fails to acknowledge this, but singular "They" is decades older than using "You" instead of "Thou" as a singular second-person pronoun. It was already in common use way back in Shakespeare's time. If thou thinkst this confusing, change thyself before demanding others change for thine own comfort.

Also, some people are plural, so the ambiguity of "they" is inclusive to them.

Also-also, the only other pronouns in common use that aren't explicitly gendered are "it/its", which some people find dehumanizing. Nonbinary and agender folks often (but not exclusively) prefer "they/them" over "it/its" or neopronouns.

Also-also-also, "picking new words to use" is extremely non-trivial for pronouns because it requires the entire English-speaking population to relearn fundamental communication habits. It's much easier to simply accept the fact that singular they is extremely common.

Thou shouldst campaign for the resurgence of a second person singular pronoun as well.

This is typical for the English language.

There used to be thou, which was a singular form of you. However, thou also implied you were talking to someone at or lower that you were. Eventually, it became seen as rude to call someone thou, so its usage dropped in favor of a uniform you.

A singular they fits this role, as the gender isn't defined enough to use he or she and the use of it would be seen as an insult.

confusing and difficult

It's really not, if you try. Have you tried? No. So give it an earnest shot before you lament your woes and push for others to bend over backward for you.

It is much quicker to understand they as a neutral instead of introducing new language and trying to disseminate that through textbooks. This way, there's no need for any (or many) edits, we can just maintain existing grammar with new understanding.

English already has another form which refers to singular and plural: 'you'. I assume that people who suddenly take umbrage are just kicking up a fuss for the sake of it, or simply didn't stop to think about what they've been using all this time.

why use many word when few word do trick?

Good grief, this is not new. It's part of the English language. They/them has always been around to use when one couldn't, or didn't want to use a more specific pronoun. Cumbersome, maybe, but much language is. It is NOT a big deal.

Entering academia early 2000s, I saw people refer to authors of research papers as "they" as a default to sidestep gendering.

On one hand it's nice to not insert gender where it isn't needed, but on the more practical hand it wasn't always possible to tell by name either. European names can have different gender in different regions, or be all Sztrkökla, and names from Asia are even harder to guess.

I totally get your opinion, because I used to share it and even created a similar post on Reddit a few years ago. Just start using it and you'll be surprised how quickly it becomes natural. There's no good reason not to do something that is easy and can potentially prevent people from feeling uncomfortable.

We don't need a new word. "Dude" already exists.

I'm a dude.

He's a dude.

She's a dude.

We're all dudes!