given that there are still plenty of passionate fans who would have done it for free
I'd imagine this is a non-starter from a corporate standpoint. I know if I were in charge I'd be terrified of the idea of just trusting community-submitted subtitles to not have random slurs or something inserted. That said I still think it would be super cool if they'd let people source and use their own subtitle files; I now it's possible because I have a tampermonkey script that lets me do just that.
That's quite the assertion. How exactly do you suggest they're buying the rights to distribute the shows then?