Their continued availability makes little sense to me.
I do think many (I dare say most) guests do use FP, and book them in advance.
I had a friend go last April and she'd never been. She had already bought tickets and knew about FP before even speaking to me. She got advice from me on booking them but she was aware and starting the process, just based on info from the Disney site.
And a coworker went a couple months ago and he was doing the same, he knew about FP and was working on their plans before we spoke about recommendations.
Neither of those are message board members
But, these passes are lasting longer than other E ticket type attractions. Maybe they built in more capacity than usual, since they were built with FP+ in mind? Honestly no idea. I do find it curious