I wanna say Scrivener exists - or at least it did in the first place - because it was a "scratch your own itch" kind of project. New versions are pretty rare, it's twelve years old and only on version 3. Checking their 'about us' page (https://www.literatureandlatte.com/about-us) confirms that; the founder learn to program explicitly to make the

There's a total of twelve people listed on that about page, only three of whom are programmers. Most of them are also writers, including two of the programmers, and it sort of sounds like a lot of these jobs are part-time.

So yeah, definitely lifestyle business rather than unicorn.