They're invested enough in it to use it, is my guess.
People tend to downplay the "neat" factor in productivity tools--and they can be total attractive nuisances where you play with them instead of doing stuff. But the truth is you do sometimes need something to keep you engaged in the short term while the long-term benefits add up. Wrestling with Notepad works against that.
FWIW, when I try to use Notepad for this, I end up with 150 open Notepad notes that just end up pickling/restoring with the app. I've never thought hard about it, but I suspect that happens because you naturally keep the note open all day, and often the next to refer back, but there's no obvious time to close it.
But for whatever reason it just tends to turn into a huge mess, whereas note-taking apps tend to either optimize to the idea of "everything all at once" or they manage a daily journal scroll for you somehow.
Author here... I had originally written something like, "I wrote my own tool but you might see these gains using any note tool". For whatever reason, I edited that out. Probably a mistake, given your confusion.
Ah, I didn't even realize this was a post/ad about a specific tool that the author was launching, I thought it was a general post about any "second brain tool". Sorry for that.