Why is "non-binary" a thing?

This question arises in my mind (again) while reading a Guardian piece on Hannah Gadsby, which consistently uses the PC approved "they" and "their" pronouns.

The other insistently "non-binary" person I read occasionally is the grievance whirlpool Sandy O'Sullivan (on Twitter), who always seems to be on the edge of a nervous breakdown.  

Oh, and some female soccer person was in the news recently for "coming out" as non-binary.

What seems very, very clear, is that, not so long ago, these women could simply have called themselves "butch lesbian" (or, if they felt a vague interest in men sexually) "butch bi woman", I suppose.  Everyone would understand that this was an apt descriptor.  That is, a woman sexually attracted to other women, who presents physically (usually deliberately, at least to some degree, in terms of fashion and physicality) as somewhat masculinised, and who likely has a somewhat "non [gender] traditional" mix of interests.  

In other words, everyone would assume that she felt like neither a "typical" female or male.  

It's clear that this can come with the territory of same sex attraction - although everyone also knows that that there can be gay women (and men) who share most stereotypical gender interests - guys only attracted sexually to men but who are heavily interested in cars and motor sports and don't care for the other type of "drag" at all, for example.

Maybe you could say that "non binary" women don't want to use "butch" as a self descriptor because it could be used an insult when it first started being commonly used.  But then, queer people are supposed to be happy about how they've "reclaimed" insult and use such terms with semi ironic pride.   I mean, seriously, if "Dykes on Bikes" has been no insult for the last (I dunno?) 30 years, surely the same can be said about "butch".  

Oh look - here's a painfully long Wiki entry on the use of "butch" and "femme" categories for lesbians.

The point I am trying to make is that it's been obvious for a long, long time that some people (be they gay, bisexual, or even straight) don't feel as if they have the "typical" gender interests, and that early feminism responded to this by critiquing overly conservative attitudes as to what it meant to "act like a real woman" (or man). 

Just thinking out loud here, because I feel there are more important things to spend time reading up on, the new thing in the "gender discourse" seems to be an implicit surrender to conservative attitudes of "this is what it takes to be a 'real' man or woman", and an insistence that not feeling like being able to "fit in" to either category deserves it's own special self identity (and the basis of great insult if people don't share this form of analysis -  including using language in a way it has not been used before.)  

As such, I find it hard to credit that "non-binary" is anything other than an exercise in category building of no use other than attention seeking, and even grievance-mongering.    

Update:  Here's the nonbinary soccer player talking, and SBS trying to explain:

Non-binary refers to people who do not relate to being either exclusively male or female.

Someone who is non-binary may feel like a mixture, somewhere in between the two, or may feel that they have no gender at all.

In a video shared by Adelaide United and Pride Cup, Wilson said their perception of gender "does not fit" the traditional definitions of man or woman. 

[Well, exactly the same as a butch lesbian or fem man doesn't "fit" traditional definition.]

"For me personally, I don't really feel like I'm anywhere near that; I feel like I'm separate from it," Wilson said.

"Other non-binary people may feel between, or they may feel a bit of both, or they may have that fluidity where they flow (between).

"It's really important to understand that every non-binary person experiences this differently and they will all have their own stories and they will all feel it some way differently."

 Wilson, who uses they/them pronouns, said it is important to use the correct pronouns when speaking to people.

"Not every non-binary person is going to use they/them, they might have no preference with pronouns, they might use any.

"It's a really important thing; you don't realise how much of a difference it makes.

"I didn't realise, but finally hearing people refer to me as they/them is this phenomenal, euphoric feeling."

Seems an odd thing to get "a euphoric feeling" about, when it's basically just getting people to conform to your adoption of an invented category that was considered unnecessary until (more or less) yesterday. 

I think it's possible that this is going to go away as a thing in due course.   

Update 2:  I feel a bit guilty in that I once speculated that in trying to understand "transgender", we might be better off allowing for a third category of gender following roughly the tribal idea of "two spirit" people who inevitably feel they are a combination of the two gender "spirits".   If I have some sympathy to people in a traditional quasi-religious system calling themselves "third gender", why should I object to your (typically dismissive of religious belief) modern woman or man using "non-binary" as very similar category?   

I feel there is a difference here, somehow, but have yet to put my finger on it!