Anything that's even remotely domain specific becomes a garbled mess. Even watching documentaries about light engineering/archeology/history subjects are hilariously bad. Names of historical places and people are randomly correct and almost always never consistent.
The second anyone has a bit of an accent then it's completely useless.
I keep them on partially because I'm of the "everything needs to have subtitles else I can't hear the words they're saying" cohort. So I can figure out what they really mean, but if you couldn't hear anything I can see it being hugely distracting/distressing/confusing/frustrating.