Isn’t reading stuff on the internet more mainstream than buying things at Barnes and Noble? Not necessarily those specific things, but the notion that something needs to be physically available at a bookstore to be relevant is at best dated.
Or spend a lot of time with certain demographics. My parents don't know what ao3 is, but a couple of female coworkers are huge fans
Edit: according to [1] 93% of users are 44 or younger, and women outnumber men 10:1
[1] https://www.flowjournal.org/2023/02/fan-demographics-on-ao3/
I think you should also assume it's called "Archive of our own" because of the same sense that Woolf had in "A Room of one's own". This is our space to do our thing, precisely because if it was someone else's space sooner or later they, at least ostensibly for good reasons, prioritize something else over our thing and it's destroyed.
So it's at least not at all a coincidence that AO3's authors are predominantly women. This story of assuming that they can thrive in a shared space and then discovering that, again often for ostensibly good reason, they're not welcome to use it after all, is very familiar to women. Whether you're being thrown out of a cafe for breast feeding ("Nudity, not allowed") or turned down by employers despite having the same skills as successful male candidates ("Bound to have kids and then we'd just have to replace her anyway") it gets wearisome, better to have a place of your own.
That's an interesting perspective, I hadn't considered that the name might be a reference to A Room of One's Own.
My understanding was that the whole "of our own" thing is mostly in reference to fanfiction sites going through a predictable cycle of becoming popular followed by overmonetizing, enshittifying and losing touch with the community, which means everyone migrates to the next site which becomes popular and repeats the cycle. Hence Ao3 run by a non-profit "of our own". But that might not be the only way in which it's true. I would certainly agree that it is somewhat of a safe space for all kinds of disparaged groups, women in general being the biggest of them
If you spend a lot of time online, it would certainly seem that way.