I think it's a relatively new thing. I've been on pretty consistantly for about the past three years, and it's just popped up within the past few months. That I've seen, at least.
Not everyone, as evidenced by @Ookla the Grammatical. (I do prefer to avoid stereotyping/generalizing, though, so... um... yeah?)
This is kind of tangentially related, but I've really been wanting to share this for a while, and haven't really been able to.
So, I haven't really been super open about this as it is a little personal (I'm not actively hiding it, either, though), but I think this is as good a time/place to share as any. I'm about 90% sure I have Asperger's, which is definitely the root of many of my social issues. (I say 90 as I haven't been officially diagnosed or anything, but I've put so much time into researching the subject that I'm pretty confident in this.)
It's a very misunderstood thing, and, honestly, it's fascinating. When I first started looking into it, everything I found that listed traits of aspies and the like as, in a way, a more extreme version of what I experience. But the more I looked into it (I do a lot of reading on psychology and stuff anyways), a few things came to my attention. The biggest one was that girls with Asperger's show that differently than boys do (and more boys have it than girls). So then I started doing research into Asperger's in girls, and it seemed like it described me very accurately, and explained a whole heck of a lot.
I have a really good video by this one guy that explains a lot about Asperger's in girls (he has a lot of other stuff as well, all of which is fantastic) if anyone is interested.
And if you want just a quick summary (I'll see if I can actually write something that's short for once) I'm more than willing to give that a go as well.
There you go! That's what I've tried saying dozens of times, but never really have before! Sorry if you didn't follow my train of thought- it was a little sporadic. And it's just a weird thing to come out and say!