I think Sam Altman popularized it with his tweets during the height of OpenAI, GPT popularity ~2023. Or maybe it was already trending by then but at least for me he was the first among prominent people to be doing it.
Smartphones forced automated capitalization on us, just look at how chatlogs have changed over time. I'd suggest no-capitalization is on the downtrend, but sticks out more because everything is automatically capitalized now.
there are times i will explicitly fight that when i am typing something on a phone and want the subtle mode shift of all lowercase, it's kind of hilarious to watch myself doing that
the lack of capitalization (and occasional omission of punctuation) was already a big thing on tumblr / twitter 10 years ago, especially in some anime and LGBT-adjacent spaces. I don't think jyn got it from Sam Altman, and I don't think he had that big a role in popularizing it.
Before smartphones, it seems to have been the standard for just about every form of instant messaging. Well, morse has no capitalization and telex would typically have been uppercase-only too, but I think we can still count those?
I suspect that this is just something that happens naturally, for shorter-format messaging typing in sentence case probably offers no added readability and tends to get dropped over time.
“Sam Altman popularized written prose without capitalization by the way he posted to twitter 3 years ago” is one of the wildest takes I have ever heard
